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Presented  hy 

DR.  WILLIAM  J.  GIES^^ 

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GlES  FELLOWSHIP 

in  Biolo3ical  Chemistry 

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ADVANCED  LESSONS 

IN 

Practical  Physiology 

FOR 

STUDENTS  OF  MEDICINE 


By 

RUSSELL  BURTON-OPITZ 
S.  M.,  M.  D.,  Ph.  D. 

Associate  Professor  of  Physiology,  Columbia  University;   Professorial 

Lecturer   in    Physiology   in   Teachers   College  and  the 

Extension  Department  of  Columbia  University 


ILLUSTRATED 


PHILADELPHIA  AND  LONDON 

W.    B.    SAUNDERS    COMPANY 

1920 


Copyright,  1920,  by  W.  B.  Saunders  Company 


PRINTED    IN    AMERICA 

PRESS    OF 

W.    B.    SAUNDERS    COMPANY 

PHILADELPHIA 


CONTENTS 


PAGE 

Introduction 17 

General  Directions 20 

LESSON  I 

Muscle  and  Nerve 21 

Ameboid  and  Ciliary  Motion.     Methods  of  Stimulation 21 

LESSON^  II 

Muscle  and  Nerve  (Continued) 25 

Myography 25 

LESSON  III 

Muscle  and  Nerve  (Continued) 35 

Irritability,  Conductivity,  and  Elasticity  of  Muscle.      The  Power  of  Muscle 

Tissue  in  Relation  to  the  Cross-section  and  Arrangement  of  Its  Fibers    35 

LESSON  IV 

Muscle  and  Nerve  (Continued) 41 

Single  Contraction,  Summation  and  Fusion  of  Contractions.  Tetanus. 
Influence  of  Changes  in  the  Strength  of  the  Stimulus  and  Load  of  the 
Muscle 41 

LESSON  V 

Muscle  and  Nerve  (Continued) 47 

Influence  of  Temperature,  Chemicals,  and  Fatigue  Upon  the  Contraction  of 

Muscle 47 

LESSON  VI 

Muscle  and  Nerve  (Continued) 51 

Contraction    of    Human    Muscle.     Influence    of    Blood-supply.      Smooth 

Muscle 51 

LESSON  VII 

Muscle  and  Nerve  (Continued) 59 

Speed  of  the  Nerve  Impulse  in  the  Frog  and  Man.     Conduction  in  Both 

Directions 55 

LESSON  VIII 

Muscle  and  Nerve  (Continued) 59 

Conduction  in  Nerve.    Action  Current  of  Muscle  and  Nerve.     Stimulation 

of  Motor  Points 59 

LESSON  IX 

Muscle  and  Nerve  (Concluded) 63 

Electrotonus.  Cathodic  and  Anodic  Excitation.  Law  of  Unipolar  Stimu- 
lation of  Human  Muscle  and  Nerve G3 

LESSON  X 

The  Blood 67 

The  Coagulation  of  the  Blood.     Counting  of  the  Blood-corpuscles 67 

13 


14  CONTENTS 

LESSON  XI  PAGE 

The  Blood  (Continued) 73 

The  Counting  of  Human  Blood-corpuscles.  Specific  Gravity  and  Ap- 
pearance of  Blood 73 

LESSON  XII 

The  Blood  (Concluded) 77 

Medicolegal  Tests  for  Blood 77 

LESSON  XIII 

The  Heart 79 

Registration  of  the  Heart-beat.  Refractory  Period.  Extrasystole.  Ex- 
cised Heart.     Action  of  Strips  of  Ventricular  Tissue 79 

LESSON  XIV 

The  Heart  (Continued) 85 

Inhibition   and  Acceleration   of  the   Simple  Heart.     Action  of   Nicotin, 

Atropin,  and  Muscarin 85 

LESSON  XV 

The  Heart  (Continued) 89 

Stannius'  Experiment.  Staircase  Phenomenon.  Summation  of  Stimuli. 
Action  of  the  Constant  Current,  Ether,  and  Chloroform.  Dissection 
of  the  Mammalian  Heart 89 

LESSON  XVI 

The  Heart  (Continued) 91 

The  Beating  Mammalian  Heart.     Heart-block.     Fibrillation 91 

LESSON  XVII 

The  Heart  (Concluded) 95 

Percussion  and  Auscultation  of  the  Human  Heart  Under  Different  Con- 
ditions      95 

LESSON  XVIII 

The  Circulation 99 

The  Capillary  Circulation.     Conversion  of  an  Intermittent  Into  a  Constant 

Flow.     Schema  of  the  Circulation 99 

LESSON  XIX 

The  Circulation  (Continued) 103 

The  Cause  and  Velocity  of  the  Pulse.     Direct  Method  of  Ascertaining  the 

Blood-pressure 103 

LESSON  XX 

The  Circulation  (Continued) 109 

Venous  Valves.     Influence  of  Dyspnea  Upon  the  Blood-pressure.     Action 

of  Amyl  Nitrite  and  Ardenalin.     Hemorrhage 109 

LESSON  XXI 

The  Circulation  (Continued) 113 

The  Effect  of  Divi.sion  and  Stimulation  of  the  Vagus  Nerve  Upon  the  Blood- 
pressure  and  Action  of  the  Heart 113 

LESSON  XXII 

The  Circulation  (Continued) 117 

The  Vasomotor  Action  of  the  Cervical  Sympathetic,  Depressor,  and  Sciatic 

Nerves 117 


CONTENTS  15 

LESSON  XX 111  PAG.: 

The  CmcuLATioN  (Continued) 121 

The  Vasomotor  Action  of  the  Greater  Splanchnic  Nerve.     The  Vascularity 

of  the  Kidney.     Oncometry 121 

LESSON  XXIV 

The  Circulation  (Continued) 12.5 

The  Indirect  Method  of  Measuring  Blood-pressure.     Effect  of  Posture  and 

Exercise 125 

LESSON  XXV 

The  Circulation  (Concluded) 129 

The  Character  and  Velocity  of  the  Arterial  and  Venous  Pulsations.     Polyg- 

rajihy ■ 129 

LESSON  XXVI 

Respiration 133 

Mechanics  of  Respiration 133 

LESSON  XXVll 

Respiration  (Continued) : .   139 

Stethography.     Methods  of  Artificial  Respiration.     Pulmotor 139 

LESSON  XXVIII 

Respir.\tion  (Continued) 141 

Nervous  Regulation  of  Respiration 141 

LESSON  XXIX 

Respiration  (Continued) 145 

Localization  of  the  Respiratory  Center.     Placenta.     Respiration  in  the 

Fish 145 

LESSON  XXX 

Respiration  (Continued) 147 

The  Circulation  in  the  Lung  of  the  Frog.      Phenomena  of  Inflammation. 

Effect  of  Changes  in  Intrathoracic  Pressure  Upon  the  Lesser  Circuit  .  .   147 

LESSON  XXXI 

Respiration  (Concluded) 151 

Elimination  of  Carbon  Dioxid  and  Consumption  of  Oxygen 151 

LESSON  XXXII 

The  Nervous  System 155 

Reflex  Action 155 

LESSON  XXXIII 

The  Nervous  System  (Continued) 159 

Reflex  Action.     Removal  of  Cerebrum 159 

LESSON  XXXIV 

The  Nervous  System  (Continued) 163 

Stimulation  of  the  Cerebrum.      The  Function  of  the  Roots  of  the  Spinal 

Cord 163 

LESSON  XXXV 

The  Nervous  System  (Conchided) 165 

Reaction  Time 165 

LESSON  XXXVI 

The  Sense  Organs 167 

Cutaneous  and  Muscular  Sensations 167 


16  CONTENTS 

LESSON  XXXVII  PAGE 

The  Sense  Organs  (Continued) 173 

Taste,  Smell,  Hearing 173 

LESSON  XXXVIII 

The  Sense  Organs  (Continued) 179 

The  Static  and  Dynamic  Senses 179 

LESSON  XXXIX 

The  Sense  Organs  (Continued) 183 

Vision 183 

LESSON  XL 

The  Sense  Organs  (Continued) 189 

Vision 189 

LESSON  XLI 

The  Sense  Organs  (Continued) 193 

Vision 193 

LESSON  XLII 

The  Sense  Organs  (Concluded) 199 

Vision 199 

LESSON  XLIII 

Digestion 207 

Deglutition 207 

LESSON  XLIV 

Digestion  (Continued) 209 

Secretion  of  Saliva 209 

LESSON  XLV 

Digestion  (Continued) 213 

Secretion  of  Pancreatic  Juice.     Action  of  Secretion.     Gastro-enterostomy.  213 

LESSON  XLVI 

Digestion  (Concluded) 215 

Lacteals  and  Thoracic  Duct.     Peristalsis.     Secretion  of  Bile 215 

LESSON  XLVII 

Absorption 217 

Osmosis.     Intestinal  Peristalsis,  Secretion  of  Intestinal  Juice.     Absorption 

From  the  Small  Intestine 217 

LESSON  XLVIII 

Excretion 221 

Secretion  of  Urine 221 

LESSON  XLIX 

Excretion  (Continued) 223 

Secretion  of  Sweat.     Body  Temperature 223 

LESSON  L 

Excretion  (Concluded) 225 

The  Innervation  of  the  Bladder.     Pilomotor  Reactions 225 

Demonstrations  to  be  Given  in  Connection  with  the  PRECEniNG  Lessons.   227 
Weights  and  Measures 229 


Index 231 


ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 


INTRODUCTION 


In  order  to  prepare  the  medical  student  for  the  clinical  work  that 
is  to  follow  during  his  subsequent  years  of  study,  the  subject  of  physi- 
ology must  be  presented  to  him  in  an  eminently  practical  manner. 
For  this  reason  the  purely  didactic  lectures  of  not  so  many  years  ago 
have  gradually  been  displaced  by  more  or  less  informal  discourses 
between  the  lecturer  and  students,  pertaining  more  particularly  to  topics 
of  unusual  complexity  and  clinical  value.  Furthermore,  the  experi- 
ments which  formerly  constituted  a  large  part  of  the  physiologic  lec- 
ture, have  since  been  separated  from  the  purely  didactic  subject  matter 
and  have  been  combined  into  a  continuous  course  of  practical  exercises 
and  demonstrations. 

The  earlier  "experimental  lectures"  have  failed  in  their  purpose, 
because  much  time  was  frequently  wasted  in  overcoming  technical  dif- 
ficulties not  apparent  at  the  beginning  of  the  hour,  and  because  little 
opportunity  was  afforded  the  students  to  become  acquainted  with 
the  apparatus  and  the  technic  required  to  perform  physiologic  experi- 
ments. These  difficulties  have  been  met  in  large  part  by  instituting 
a  course  in  practical  physiology,  designed  so  that  the  student  himself 
may  perform  simple  and  instructive  experiments.  Obviously,  the  ac- 
quisition of  knowledge  by  the  laboratory  method  consumes  a  longer 
period  of  time  and  requires  a  definite  experimental  aptitude  on  the 
part  of  the  student.  Furthermore,  this  method  of  teaching  entails  the 
expenditure  of  large  sums  of  money  for  apparatus  and  the  salaries  of 
additional  teachers.  These  difficulties,  however,  have  been  overcome 
in  recent  years  in  all  the  schools  of  higher  grade,  and  practical  courses 
in  physiology  are  now  an  accomplished  fact,  and  rightly  so,  because  the 
benefits  which  the  students  derive  from  work  of  this  kind  cannot  be 
overestimatctl.  -  It  cultivates  the  faculty  of  close  observation  and  ac- 
curate rating  of  facts.  It  develops  the  power  of  logical  thought  and 
expression,  and  impresses  upon  them  facts  and  principles  otherwise 
scarcely  noted  and  comprehended.  Indeed,  many  students  nnist  see 
things  in  order  to  be  able  to  obtain  a  clear  mental  picture  of  them,  but 
when  once  seen,  the  impression  is  lasting.  Where  else  than  in  medicine 
could  this  manner  of  teaching  be  of  greater  service? 

Quite  aside  from  the  fact  that  this  method  constitutes  an  admirable 
means  of  imparting  physiologic  knowledge,  it  also  enables  the  students 

2  17 


18  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

to  familiarize  themselves  with  the  use  of  operative  instruments  and  the 
action  of  different  drugs.  During  a  course  of  this  kind  each  student  is 
repeated^  called  upon  to  attend  to  the  narcosis;  to  perform  trache- 
otomj^;  to  expose  and  ligate  blood-vessels,  and  to  isolate  nerves  and 
other  structures.  It  need  scarcely  be  emphasized  that  the  operative 
technic  acquired  by  him  upon  animals  under  test  conditions,  will  serve 
hmi  in  good  stead  later  on  when  forced  to  repeat  these  procedures  upon 
human  beings. 

The  contention  that  students  may  derive  their  knowledge  of  physi- 
ology wholly  from  practical  work,  is  scarcely  worthy  of  consideration. 
While  the  average  student  is  well  able  to  abstract  definite  single  facts 
from  experiments,  he  is  as  yet  in  no  position  to  appraise  these  facts  and 
to  combine  them  into  a  connected  story  of  physiologic  events.  Knowl- 
edge gained  by  experunentation  alone  is,  indeed,  very  fragmentary. 
It  is  the  duty  of  the  lecturer  to  bridge  over  these  defects  and  to  supply 
the  student  with  those  fundamental  data  which  he  is  to  make  use  of 
later  on  in  formulating  physiologic  principles.  Facts,  as  such,  are  of 
little  value  unless  they  can  be  joined  to  yield  certain  truths  which  have 
a  dii-ect  bearing  upon  the  student's  subsequent  clinical  work.  The 
student  should  be  made  to  "physiologize"  along  lines  more  closely  re- 
lated to  his  chosen  profession  and  should  attain  this  state  in  as  short  a 
time  as  possible.  In  many  instances  this  mental  evolution  may  be 
greatly  facilitated  by  referring  to  problems  of  general  interest,  such  as 
may  be  obtained  from  treatises  upon  comparative  physiology,  biology, 
physics,  and  chemistry.  Comparative  physiology,  in  particular,  is  very 
rich  in  facts  which  will  greatly  aid  the  lecturer  in  clearing  up  doubtful 
or  complex  points  in  special  physiology. 

In  the  medical  schools  of  higher  grade  about  three  hundred  hours 
are  allotted  to  physiology,  exclusive  of  physiologic  chemistry  and 
clinical  physiology  or  experimental  medicine.  This  period  of  time  is 
spent  in  part  in  the  laboratory  and  in  part  in  the  lecture  room.  As  a 
rule,  one  hundred  and  eighty  hours  are  assigned  to  practical  work  and 
one  hundred  and  twenty  hours  to  lectures  and  conferences.  Inasmuch 
as  the  academic  year  usually  comprises  thirty  weeks,  exclusive  of  the 
time  set  aside  for  examinations,  the  above  enumeration  leads  us  to  infer 
that  each  student  must  devote  ten  hours  per  week  to  physiology.  In 
many  institutions,  however,  the  ''concentrated"  system  of  teaching  is 
employed,  enabling  the  student  by  constant  daily  attendance  to  com- 
plete his  work  in  phj^siology  within  about  four  months — similar  periods 
of  time  being  set  aside  for  anatomy  and  physiologic  chemistry. 

Before  submitting  these  lessons  in  practical  physiology  to  the  stu- 
dents I  should  like  to  mention  that  I  have  attempted  to  embody  in 
them  all  those  experiments  which  can  be  conveniently  performed  with 
the  aid  of  simple  apparatus.  The  lessons  begin  with  experiments 
upon  muscle  and  nerve,  and  gradually  make  a  greater  and  greater 
demand  upon  the  experimental  aptitude  of  the  student.  Those  experi- 
ments which  require  complex  apparatus  and  may  be  more  conveniently 


INTRODUCTION  19 

displa^'cd  to  a  large  number  of  students,  have  been  embodied  in  the 
demonstrations.  A  brief  list  of  experiments  of  this  kind  is  given  on 
pages  227,  228. 

While  it  is  difficult  to  perform  physiologic  experiments  in  accordance 
with  a  definite  time-schedule,  the  material  embodied  in  this  book  has 
been  arranged  in  such  a  way  that  each  lesson  will  require  about  three 
hours  for  its  completion  and  each  demonstration  one  hour,  making  a 
total  of  one  -iiundrod  and  eighty  hours.  At  the  end  of  each  period  a 
few  minutes  should  Ije  set  aside  for  a  review  of  the  work  performed. 
Special  attention  should  at  this  time  be  paid  to  those  students  who  have 
failed  to  observe  and  formulate  the  essential  facts  and  principles  to  be 
derived  from  any  particular  lesson.  It  would  be  a  pedagogically  un- 
sound principle  to  call  the  attention  of  the  students  to  these  facts  before- 
hand, because  introductory  explanations  tend  to  rob  the  student  of  the 
pleasure  of  independent  investigation  and  thought.  If  the  work  in 
physiology  is  well  balanced  and  co-ordinated  between  the  class-room 
and  the  laboratory,  preliminary  talks  pertaining  to  the  general  bearing 
of  the  different  experiments  are  actually  worse  than  useless.  Such 
discussions  should  concern  themselves  more  particularly  with  matters 
closely  related  to  the  methods  and  apparatus,  so  that  the  student  may 
be  in  a  more  favorable  position  to  avoid  mistakes  in  his  technic.  I  have 
endeavored  to  aid  him  in  this  regard  by  supplying  him  with  this 
laboratory  guide,  amplified,  for  the  reason  just  stated,  with  explana- 
tions bearing  directly  upon  the  experiments. 

R.  Burton-Opitz. 

Columbia  University, 
May,  1920. 


GENERAL  DIRECTIONS 

Each  class  of  students  should  be  divided  into  sections  of  not  more 
than  40  each.  To  each  section  should  be  allotted  4  assistants,  so  that 
each  assistant  may  be  held  responsible  for  the  work  of  10  students, 
arranged  in  pairs.  A  larger  number  than  this  cannot  well  be  attended 
to  by  one  instructor. 

When  mammals  are  being  used,  as  many  as  8  students  may  be 
assigned  to  one  operating  table.  The  formation  of  larger  groups  is 
not  to  be  recommended,  because  it  lessens  the  chances  of  the  individual 
student  to  perform  a  considerable  part  of  the  work  himself.  Neither 
does  it  seem  advisable  to  decrease  this  number  materially,  owing  to 
the  fact  that  such  reduction  would  necessitate  an  extra  expenditure  for 
apparatus  and  material  which  is  not  proportional  to  the  increase  in  the 
efficiencj^  of  the  teaching.  Since  the  work  of  the  students  requires 
close  supervision,  one  assistant  should  be  assigned  to  each  operating 
table.  If  an  additional  table  is  put  in  use,  these  students  should  re- 
ceive the  necessary  attention  from  the  instructors  at  the  two  neighbor- 
ing tables. 

The  function  of  the  instructor  is  to  advise  the  students  how  to 
proceed,  and  to  guide  them  by  pertinent  questions  and  practical  hints 
through  the  work  assigned  to  them.  Nothing  should  be  told  the  stu- 
dents which  they  can  readily  discover  for  themselves,  and  nothing 
should  be  done  for  them  which  they  can  conveniently  do  themselves. 
At  least,  this  plan  of  teaching  should  be  followed  as  soon  as  the  students 
have  received  their  first  instruction  in  etherization,  in  performing  trache- 
otoni}',  and  in  exposing  different  blood-vessels.  A  record  should  be 
kept  of  the  work  done  by  each  student  during  every  exercise,  so  that 
a  different  task  may  be  assigned  to  him  during  the  succeeding  exercise. 

Each  student  should  make  brief  entries  in  his  note-book  pertaining 
to  the  results  and  bearing  of  the  experiments  performed  by  him.  In 
addition,  this  book  should  contain  diagrams  of  the  apparatus,  explana- 
tory schemas,  and  the  curves  recorded  by  him  in  the  course  of  these 
practical  exercises. 

Each  pair  of  students  should  be  in  possession  of  a  set  of  operating 
instruments,  embracing  two  pairs  of  forceps,  two  pairs  of  scissors  of 
different  size,  and  two  scalpels  of  different  size.  Ligatures,  sponges, 
ether,  and  towels  will  be  supplied  by  the  attendant.  A  rubber  apron 
should  be  worn  by  every  student  during  the  experiments  upon  mam- 
mals. Dissecting  gowns  and  instruments  are  not  regarded  with  favor 
in  the  phj'siologic  laboratory. 

At  the  end  of  each  session  the  apparatus  is  to  be  taken  apart  and 
each  piece  carefully  cleaned.  Special  receptacles  are  provided  for  the 
discarded  organic  material. 

20 


LESSON  I 

MUSCLE  AND  NERVE 

AMEBOID  AND  CILIARY  MOTION.    METHODS  OF  STIMULATION 

1.  Ameboid  Motion. — Place  a  few  drops  of  a  hay  infusion  upon  a 
glass  slide.  Bring  a  large  and  active  ameba  into  the  field  of  the  micro- 
scope. Observe  carefully  the  behavior  and  position  of  the  organism, 
making  drawings  of  its  shape  at  regular  intervals.  Add  a  few  granules 
of  India-ink  to  the  medium  and  observe  how  these  particles  are  engulfed. 

2.  Protoplasmic  Streaming.^ — Examine  with  the  low  power  of  a 
microscope  a  leaflet  of  a  fresh  specimen  of  nitella.  Observe  the  move- 
ment of  the  protoplasm.  What  part  of  the  cell  is  in  motion?  In  which 
direction  does  the  flow  take  place?  How  is  the  movement  changed  by 
mechanical  stimuli?     Note  the  effect  of  warmth  upon  the  movement. 

3.  Ciliary  Motion. — Etherize  a  frog  and  destroy  its  brain  and  spinal 
cord.  Place  the  animal  upon  its  back.  Make  a  median  incision  through 
the  lower  jaw,  and  retract  the  segments  laterally.  Place  a  small  piece 
of  cork  upon  the  mucous  surface  between  the  eyes.  Moisten  the  sur- 
face with  normal  saline  solution,  if  necessary.  Note  how  the  piece  of 
cork  is  gradually  carried  by  the  action  of  the  cilia  toward  the  esophagus. 
Determine  its  rate  of  movement.  Moisten  the  surface  with  normal 
saline  solution  the  temperature  of  which  has  been  raised  2  or  3  degrees 
above  that  of  the  room.  Note  the  effect  upon  the  movement  of  the 
cork. 

Tilt  the  plate  upon  which  the  frog  is  resting  until  the  cilia  are  no 
longer  able  to  move  the  piece  of  cork.  Hold  the  plate  horizontally  and 
put  small  bits  of  lead  upon  the  cork  until  one  is  found  which  the  cilia 
are  unable  to  propel.  What  is  your  idea  regarding  the  strength  of  these 
structures? 

Place  a  small  segment  of  the  gill-plate  of  a  fresh  clam  upon  a  slide 
for  microscopic  observation.  Straighten  its  edge  and  immerse  the 
entire  preparation  in  a  few  drops  of  the  fluid  obtained  when  the  shell 
of  the  clam  was  opened.  Study  carefully  the  action  of  the  cilia  at  in- 
tervals, and  especially  later  on,  when  their  movement  has  been  consider- 
ably slowed  so  that  single  cilia  may  l)e  clearly  made  out.  What  is  the 
position  of  the  cilia  when  at  rest  and  when  contracting?  Apply  normal 
saline  solution  which  has  been  slightly  heated  (25°  C).  Note  its  effect 
upon  the  rapidity  of  the  movement. 

4.  Structure  of  the  Dififerent  Types  of  Muscle  Tissue. — Unless  still 
quite  familiar  with  the  general  structure  of  non-striated,  striated,  and 
cardiac  muscle,  examine  preparations  of  these  tissues  under  the  micro- 
scope.    Study  the  action  of  the  myoids  in  stentor  or  vorticella. 

21 


22  ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 

5.  Muscular  Movement.— With  a  small  blunt  instrument  scrape  off 
the  wing  muscles  of  a  beetle  (hydrophilus)  and  place  them  upon  a  slide 
for  microscopic  study.  Observe  the  waves  of  contraction  passing  over 
the  individual  muscle-fibers.  Note  the  increase  in  the  diameter  of  the 
fiber  at  the  point  of  contraction. 

6.  Stimuli.  Muscle-nerve  Preparation. — Living  substance  possesses 
the  properties  of  irritability,  conductivity,  and  contractility,  i.  e.,  it  is 
capable  of  receiving  a  stimulus,  of  conducting  it  to  some  other  part 
of  its  substance,  and  of  reacting  toward  it  in  accordance  with  its  struc- 
tural peculiarities.     A  stimulus  is  any  extraordinary  change  in   the 


Fig.  1. — Muscles  of  Hind  Leg  of  Frog.     (Ecker.) 

environment  of  the  living  entity,  in  consequence  of  which  it  evolves 
some  form  of  energy.  In  this  way  a  muscle  may  be  made  to  contract 
and  a  gland  to  secrete.  As  a  matter  of  convenience  we  usually  employ 
the  former  tissue  and  principally  that  derived  from  the  frog. 

Grasp  the  pelvis  of  a  lightly  etherized  frog  between  the  thumb  and 
index-finger  of  your  left  hand,  allowing  the  ventral  aspect  of  the  thorax 
and  head  to  rest  upon  your  third  and  fourth  fingers.  With  your  right 
hand  move  the  point  of  a  small  scalpel  rapidly  backward  from  between 
the  eyes  until  you  feel  a  depression  at  the  junction  of  the  head  with  the 
spinal  column.     This   depression   lies   at   the  atlo-axoid  articulation. 


MUSCLE    AND    NERVE  2'^ 

Gently  pross  tho  point  of  tho  scjilpol  ti-:msvorse!y  into  this  opening, 
dividinji;  the  si)in;il  cord.  Introduce  ;i  seeker  throufi;li  the  incisi(jn,  and, 
passing  it  upward  into  the  cranial  cavity,  quickly  destroy  the  cerebrum. 
Reverse  the  direction  of  the  seeker  and  pass  it  downward  through  the 
vertebral  canal,  destroying  the  cord.  This  operation  should  consume 
only  a  few  seconds  of  time.  It  is  known  as  pithing,  and  corresponds  to 
the  destruction  of  the  spinal  cord  of  mammals  by  the  excessive  flexion 
of  the  head  npon  the  spinal  column.  The  odontoid  process  of  the  axis 
then  lacerates  the  cord. 

Amputate  one  leg.  Remove  the  skin  from  the  thigh  and  isolate 
the  sciatic  nerve.  Cut  away  the  muscles  of  the  thigh,  })ut  preserve  the 
femur  and  nerve.  Suspend  the  leg  from  a  clamp  fastened  horizontally 
to  an  iron  stand  by  fixing  the  femur  in  its  screw  clip.  Attach  the 
central  end  of  the  sciatic  nerve  to  a  needle-holder  and  moisten  the 
preparation  with  an  isotonic  solution  of  sodium  chloric!  (0.7  per  cent.). 

7.  Direct  and  Indirect  Stimulation  of  Muscle. — Use  the  following 
means  to  cause  a  contraction  of  the  calf  muscle  (gastrocnemius) : 

(a)  Mechanical  stimulation.  Pinch  the  end  of  the  nerve  with  the 
forceps. 

(6)  Chemical  stimulation.  Dip  the  end  of  the  nerve  in  a  strong 
solution  of  sodium  chlorid.    Cut  away  the  piece  of  the  nerve  used. 

(c)  Thermal  stimulation.  Heat  a  piece  of  wire  and  bring  it  in  con- 
tact with  the  nerve. 

{d)  Electric  stimulation.  Apply  the  electrodes  from  the  secondary 
coil  of  an  inductorium  to  the  nerve.  Close,  and  open  the  key  inserted 
in  the  primary  circuit. 

(e)  Photic  stimulation.  Under  these  conditions  rays  of  light  do  not 
serve  as  a  stimulus. 

Place  your  index-finger  under  the  sole  of  the  foot  and  repeat  the 
electric  stimulation.  Explain  the  action  of  the  gastrocnemius  muscle. 
Remove  the  skin.  Stimulate  the  muscle  directly.  Which  stimulation 
is  more  effective? 

Locate  the  tendo  achillis.  Carefully  dissect  the  other  leg  and  iden- 
tify the  sartorius  and  gracilis  muscles.  Open  the  abdomen  of  the  frog 
and  trace  the  sciatic  nerve  to  its  point  of  origin  from  the  spinal  cord. 


LESSON  II 


MUSCLE    AND   NERVE  (Continued) 
MYOGRAPHY 

1.  The  Construction  and  Action  of  the  Dry  Cell. — The  electric 
method  of  stimulation  is  employed  most  frequently  in  the  laboratory 
because  it  is  the  most  convenient.  The  electric  enereiy  is  derived,  as  a 
rule,  from  a  Voltaic  cell.  As  a  generator  may  be  employed  a  Daniell, 
Grove,  or  Leclanch6  cell.  The  moist  cells,  however,  have  been  dis- 
placed in  the  course  of  time  by  the  so-called  dry  cells  which  give  off  no 
fumes  and  acids,  need  no  refilling,  and  give,  as  a  rule,  good  service  at 
slighter  cost.  The  dry  cell  connnonly  used 
is  a  modification  of  the  Leclanche  cell.  It 
consists  of  a  jacket  of  zinc  lined  with  plaster 
of  Paris  and  saturated  with  ammonium 
chlorid.  Its  inner  space  is  taken  up  by  a 
carbon  plate  which  is  surrounded  by  black 
oxid  of  manganese.  The  plate  of  carbon 
projecting  from  this  mixture  forms  the  posi- 
tive pole  or  anode,  whereas  the  negative  pole 
or  cathode  is  represented  by  the  zinc. 

Electricity  "flows"  from  a  place  of  high 
potential  to  a  place  of  low  potential.  Hence, 
if  the  carbon  and  zinc  of  the  battery  are  con- 
nected by  means  of  a  conductor,  say,  a  copper 
wire,  a  current  is  set  up  which  leaves  the 
generator  at  the  former  pole  and  enters  it 
at  the  latter.  Inside  the  cell  the  current 
flows  from  the  zinc  to  the  carbon  to  complete 
the  circuit  (Fig.  2). 

The  difference  in  the  potential  between 
the  two  poles  of  a  battery  constitutes  the 
electromotive  force.  It  is  maintained  by  the 
interaction  of  the  chemical  substances  con- 
tained in  the  battery.  The  latter,  therefore, 
corresponds  to  a  reservoir  of  electricity  which  remains  filled  as 
long  as  there  is  enough  material  present  to  yield  chemical  energy. 
When  this  material  has  been  used  up,  the  difference  in  the  electric  po- 
tential disappears  and  the  current  ceases. 

In  its  passage  through  wires  the  electric  current  loses  a  certain 
amount  of  its  initial  energy,  owing  to  the  resistance  which  it  must  first 
overcome.     Consequently,  the  strength  of  a  current  or  the  rate  of  flow 


Fig.  2. — Diagram  of 

Daniell  Cell. 
Cu,  Copper  plate  (+);  Z, 
zinc  plate  ( — ).     The  direc- 
tion  of  the   current  is  indi- 
cated by  the  arrows. 


26  ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 

of  electricity  between  two  different  points  of  the  conducting  path  is 
dependent  not  onl}^  upon  the  electromotive  force  but  also  upon  the 
resistance  of  the  conductor.  A  short  and  thick  wu-e  possesses  less 
resistance  than  a  long  and  thin  wire;  hence,  provided  that  the  electro- 
motive force  remains  constant,  the  flow  of  electricity  will  be  greater 
in  the  first  instance.  Besides  this  external  resistance  encountered  by 
the  current  in  its  passage  from  the  copper  to  the  zinc,  it  is  also  opposed 
b}'-  an  internal  resistance  resident  in  the  constituents  of  the  battery. 
In  the  latter  case,  the  resistance  is  the  less  the  larger  the  surface  of  the 
plates. 

A  unit  of  current  is  designated  as  an  ampere,  a  unit  of  electromotive 
force  as  a  volt,  and  a  unit  of  resistance  as  an  ohm.  An  ohm  equals  the 
resistance  of  a  volume  of  mercury  1  mm.  in  area  and  1063  mm.  in 
length  at  0°  C.  The  electromotive  force  of  a  Daniell  cell  is  about 
1  volt  and  that  of  an  ordinary  dry  cell  1.5  volt. 

The  relationship  existing  between  these  different  factors  is  expressed 

by  Ohm's  law,  in  accordance  with  which  the 

,     ,        ^,         electrom.  force  volts 

current  strength  =  : ; or  amperes  =  

mt.  res.  and  ext.  res.  ohms 

Any  one  of  these  factors  may  be  determined  as  follows : 

volts        =  amperes  X  ohms 

amperes  =  volts        -^-  ohms 

ohms       =  volts        -^  amperes 


Fig.  3. — Mercury  Key. 

2.  The  Simple  Key. — Living  substance  may  be  stimulated  with  an 
electric  current  by  simply  touching  it  with  the  ends  of  the  loose  wires 
leading  out  from  the  poles  of  a  battery.  A  better  way,  however,  is  to 
leave  the  wires  in  firm  contact  with  the  living  substance  and  to  stimu- 
late it  by  making  and  breaking  the  current  by  means  of  a  key.  Three 
kinds  of  keys  are  commonly  used  in  the  laboratory,  namely,  mercury, 
friction  (DuBois-Reymond),  and  automatic  keys. 

The  mercury  key  consists  of  a  round  wooden  base  weighted  with 
iron.     The   center  of  its  upper  surface  is   depressed  for  the  recep- 


MUSCLE   AND    NERVE 


2- 


tion  of  a  small  vulcanite  cup  which  is  partially  filled  with  mercury. 
To  the  sides  of  the  wooden  base  are  attached  two  brass  rods.  The 
inner  ends  of  these  dip  into  the  mercury,  while  their  outer  ends  are 


Fig.  4. — Morse  Key. 

connected  by  means  of  binding-posts  with  the  poles  of  the  battery. 
One  of  these  rods  is  jointed  so  that  its  inner  end  may  be  dipped  into 
the  mercurj'-  or  removed  from  it  at  will,  thereby  making  and  breaking 
the  current.  The  friction  key  consists  of 
a  vulcanite  base  to  which  are  attached 
two  oblong  bars,  II  and  III,  each  of  which 
is  equipped  with  two  binding-posts.  Bars  II 
and  III  are  joined  by  a  third  bar,  IV,  which 
is  jointed  at  one  end  and  may  be  elevated 
at  its  other  end,  thereby  breaking  the 
contact  between  II  and  III.  On  lowering 
this  bridge  the  current  is  made,  while  on 
raising  it  it  is  broken.  The  automatic  key 
presents  many  forms.  It  consists,  as  a 
rule,  of  a  rotating  disk  to  which  are  at- 
tached a  number  of  contacts.  Since  the 
speed  of  the  disk  and  the  position  of  these 
contacts  may  be  varied,  it  is  possible  to 
make  and  break  the  circuit  without  effort 
and  at  definite  intervals. 

3.  Stimulating  Electrodes. — The  elec- 
tric current  may  l)e  conve3Td  through 
living  matter  by  simply  applying  the  ends 
of  the  copper  wires  to  its  surface.  The 
closure  of  the  key  then  completes  the 
circuit  from  carbon  to  zinc.  ]\Iost  com- 
monly, however,  the  ends  of  the  copper 
wires  are  brought  close  together  and  soldered  to  platinum  points.  They 
are  then  placed  within  a  narrow  piece  of  hard  rubber,  so  that  they  can 
be  conveniently  handled.  This  form  of  electrode  cannot  be  used  for 
a  long  time,  because  the  conduction  of  an  electric  current  through  moist 


Fig.  5. — Friction  Key. 


28 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


conductors,  such  as  are  presented  by  animal  tissue,  invariably  leads 
to  a  polarization  of  the  current.  The  two  metals  of  the  battery,  copper 
and  zinc,  are  smTOunded  by  electrolytes,  the  tendency  of  which  is  to 
pass  toward  the  opposite  pole.  Thus,  the  positive  ions,  Cu  and  H, 
progress  toward  the  cathode,  whereas  the  OH  and  SO4  pass  toward 
the  anode,  which  inside  the  cell  is  the  zinc.  Presently  the  copper  plate 
becomes  covered  with  bubbles  of  H,  which  place  a  high  resistance  in 
the  path  of  the  current  and  eventually  neutralize  it.  This  phenomenon 
is  known  as  polarization. 

A  similar  action  takes  place  at  the  points  of  contact  between  the 
electrodes  and  the  tissue.  It  may  be  prevented  by  the  use  of  the  so- 
called  non-polarizable  electrodes.  Those  devised  by  DuBois-Reymond 
consist  of  zinc  terminals  immersed  in  a  solution  of  zinc  sulphate.     A 


Fig.  6. — Stimulating  Electrodes. 
A,  B,  and  C,  Boot  electrodes;  D  and  E,  clinical  electrodes;  F,  hand  electrodes. 

Apparatus  Co.) 


{Harvard 


very  simple  form  may  be  constructed  by  taking  two  pieces  of  glass  tub- 
ing, measuring  4  mm.  in  diameter  and  6  mm.  in  length.  One  end  of 
each  tube  is  filled  with  modeling  clay  moistened  with  normal  saline 
solution.  Above  the  plug  the  tube  is  filled  with  a  saturated  solution 
of  sulphate  of  zinc  into  which  is  placed  a  short  rod  of  amalgamated  zinc 
carrying  the  ends  of  the  copper  wires.  The  points  of  contact  with  the 
tissue  are  wrapped  in  cotton  moistened  with  saline  solution.  These 
electrodes  must  be  immersed  in  saline  solution  for  some  hours  before 
they  are  used  so  as  to  render  the  clay  permeable  (Fig.  7). 

4.  The  Different  Types  of  Electric  Currents. — If  the  two  poles  of  a 
battery  are  connected  with  one  another  by  wires  and  a  simple  key,  the 
current  begins  to  flow  as  soon  as  the  bridge  has  been  closed,  and  ceases 
to  flow  after  the  latter  has  been  opened.     The  strength  of  this  current 


MUSCLE    AND    NERVE 


29 


remains  the  same  as  long  as  the  electromotive  force  and  the  resistance 
do  not  change.  A  current  of  this  kind  is  known  as  a  constant  or  gal- 
vanic current. 

If  a  coil  of  insulated  wire  is  arranged  around  a  ring  of  iron,  it  will 
be  found  that  the  passage  of  a  constant  current  through  the  iron  sets 
up  an  electric  variation  in  the  outside  spool  of  wire.  This  secondary 
current,  however,  develops  only  on  the  make  and  break  of  the  primary 
current  traversing  the  iron.  An  electric  energy  appearing  in  this  form 
is  called  an  induced  current.  Moreover,  since  the  primaiy  current  may 
be  made  and  broken  at  long  and  short  intervals,  we  recognize  single 
make  and  break  shocks  and  rapidly  repeated  shocks.  The  latter  form 
the  so-called  quickly  interrupted  or  "tetanic"  current.  It  will  be  noted 
that  the  induced  current  is  independent  of  the  primary  current,  and 


Fig.  7. — Non-polarizable  Electrodes. 
M,  Muscle  or  nerve;   C,  cotton  or  camel's-hair  brush;  S,  solution  of  zinc  sulphate;   Z, 

amalgamated  zinc. 

develops  only  on  the  make  and  break  of  the  primary  current.  In  be- 
tween these  two  points  no  induction  takes  place,  although  the  primary 
current  continues  to  flow. 

5.  The  Induction  Coil.— The  apparatus  by  means  of  which  the 
induced  current  is  obtained  is  known  as  an  inductorium.  It  consists 
of  about  130  coils  of  insulated  copper  wire  of  medium  thickness,  the 
terminals  of  which  are  connected  with  a  key  and  the  two  elements  of 
a  battery.  These  connections  constitute  the  primary  circuit.  The 
core  of  the  primary  coil  is  filled  with  a  bundle  of  iron  wire  coated  with 
shellac.  A  second  spiral  consisting  of  about  6000  coils  of  insulated 
copper  wire  of  a  thickness  of  6.1  mm.  is  adjusted  around  the  primary 
coil  in  such  a  way  that  it  may  be  moved  nearer  to  or  farther  away  from 
the  primary.     The  two  ends  of  the  secondary  wire  are  fastened  to 


30 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


binding-posts  which,  in  turn,  may  be  connected  with  the  stimulating 
electrodes.  These  connections  constitute  the  secondary  circuit  of  the 
inductorium.  As  has  been  stated  above,  the  making  and  breaking  of 
the  primary  current  gives  rise  momentarily  to  an  induced  current  in 
the  secondary  coil. 

A  rapid  interruption  of  the  primary  current  may  be  effected  by 
closing  and  opening  the  key  in  quick  succession  with  the  hand.     A 


#-<.V'w^-'WV*    > 


K 


Fig.  8. — The  Inductobixjm. 
/,  Primary  circuit  and  coil;  //,  secondary  coil  and  circuit;  K,  key;  j,  automatic  inter- 
rupter; n,  nerve. 

more  convenient  means,  however,  is  afforded  by  such  automatic  inter- 
ruptors  as  have  been  described  by  Neef.  The  latter  mechanism  con- 
sists of  a  vibrating  rod  and  magnet,  both  of  which  are  attached  to  the 
end  of  the  inductorium.  A  glance  at  Fig.  10  will  show  that  the  current 
from  the  battery  (A)  is  led  into  pillar  B  as  far  as  the  platinum  contact 
D  upon  the  vibrator  V.     If  the  latter  is  in  contact  with  the  end  of  the 


Fig.  9. — The  Inductorium.     {Harvard  Apparatus  Co.) 

wire  of  the  primary  coil  at  D,  the  current  will  traverse  this  spiral  {PC) 
and  return  to  pillar  F  and  the  battery  by  way  of  the  double  spiral  E. 
But  as  the  current  passes  through  spirals  E  their  iron  cores  are  mag- 
netized and  attract  the  iron  plate  H  of  the  vibrator  F,  thereby  break- 
ing the  contact  at  D.  When  the  primary  current  is  broken  in  this 
manner  the  spirals  (E)  are  again  demagnetized.  This  plate  {H)  being 
released,  the  vibrating  rod  moves  upward  and  again  makes  contact 


MUSCLE    AND    NERVE 


31 


at  D.  'At  the  moment  when  the  priiiuuy  current  is  made  and  broken 
an  induced  current  is  momentarily  developed  in  the  secondary  coil. 

6.  Stimulation  of  Muscle  and  Nerve — The  Condant  Current. — Con- 
nect in  scries  two  dry  cells  and  a  sunplc  key  and  apply  the  ends  of  the 
wires  leading  away  from  them  to  the  tongue.  Make  and  break  the 
current  by  closing  and  opening  the  key.  When  do  you  perceive  the 
stimuli?  Note  that  the  make  shock  is  the  stronger  of  the  two.  Does 
the  current  stimulate  while  it  continues  to  flow,  i.  e.,  between  the  make 
and  break? 

Upon  the  basis  that  a  stimulus  arises  in  consequence  of  any  extra- 
ordinary change  in  the  environment,  it  may  be  said  that  an  electric  cur- 


FiG.  10. — The  Automatic  Interrupter  of  the  Inductorium  (Neef's). 

A,  Entrance  of  current  from  battery  into  post  B  and  vibrator  V  as  far  as  D.     In 

accordance  with  the  position  of  the  vibrating  plate,  the  current  now  flows  either  back  to 

the  battery  C  through  post  F  or  into  the  primary  coil  PC  through  D.     In  the  latter 

case,  the  current  first  traverses  magnet  E  before  it  can  reach  the  battery  by  way  of  post  F. 

rent  stimulates  only  when  its  intensity  is  rapidly  altered.  Such  altera- 
tions occur  only  on  the  make  and  on  the  break  of  the  current,  and 
hence,  no  stimulation  is  evoked  in  between  these  two  points.  Inasmuch 
as  the  full  electric  potential  is  thrown  into  the  living  substance  on  the 
make  of  the  constant  current,  the  latter  reacts  with  greater  amplitude 
at  this  time  than  later  on  (break),  when  it  has  been  partially  adapted 
to  this  stimulus. 

Single  Induction  Shocks. — Connect  in  series  two  dry  cells,  a  simple 
key,  and  posts  1  and  2  of  the  inductorium.  This  connection  does  not 
include  Neef's  automatic  interruptor,  and  hence,  the  current  may  be 
made  and  broken  at  intervals  of  varj-ing  length.     Make  and  break  the 


32  ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 

primary  current.     When  do  you  perceive  the  stimuH?     Which  stimula- 
tion is  the  stronger,  the  making  or  the  breaking  induction  shock? 

Annotation. — If  the  direction  of  the  induced  current  is  determined  by  means  of 
a  galvanometer,  it  will  be  found  that  the  making  shock  is  opposed  to  the  primary- 
current,  Avhile  the  breaking  shock  passes  in  the  same  direction  as  the  primary  cur- 
rent. Secondly,  the  make  induction  develops  more  slowly  than  the  break  induction, 
because  the  entering  primary  current  must  first  overcome  the  self-induction  in  the 
primary  coil  before  it  can  produce  a  similar  effect  in  the  secondary  coil.  As  it  passes 
from  one  tiu"n  of  the  primary  wire  to  another,  an  induced  current  is  momentarily 
set  up  in  the  secondary  coil  which  possesses  a  direction  opposite  to  the  primary. 
Its  strength  is  thereby  diminished.  On  the  break,  this  impediment  is  not  present, 
and  hence,  the  induction  in  the  secondary  coil  is  enabled  to  reach  its  maximal  value 
with  much  greater  rapidity. 

Quickly  Repeated  Induction  Shocks  or  Tetanic  Current. — Connect 
in  series  two  dry  cells,  a  key,  and  posts  1  and  3  of  the  inductorium. 
This  connection  brings  Neef  s  hammer  into  the  circuit  and  allows  us  to 
make  and  break  the  primary  current  in  rapid  succession,  thereby  pro- 
ducing an  entire  series  of  inductions.  Compare  the  stimulating  value 
of  the  quickly  interrupted  or  tetanic  current  with  that  of  single  induc- 
tion shocks. 

7.  Changes  in  the  Strength  of  the  Current. — Use  single  induction 
shocks.  Push  the  secondary  coil  of  the  inductorium  over  the  primary. 
Stimulate.  Gradually  increase  the  distance  between  the  secondary  and 
primary  coils  and  repeat  the  stimulation.  What  difference  do  you  no- 
tice?    Explain. 

Annotation. — The  strength  of  the  induction  shocks  depends  first  of  all  upon  the 
electromotive  force  of  the  primary  current.  Secondly,  it  is  proportional  to  the  separa- 
tion of  the  secondary  coil  from  the  primary,  becoming  the  weaker  the  greater  the 
distance  between  them.  The  strength  of  the  induction  current  may  be  indicated 
approximately  by  giving  the  strength  of  the  battery  and  the  distance  between  the 
coils  in  centimeters.  The  latter  may  be  read  off  directly  from  the  scale  inscribed 
upon  the  base  of  the  inductorium. 

8.  Direct  and  Indirect  Stimulation. — Suspend  the  leg  of  a  frog  from 
the  clamp  in  the  manner  described  previously  (p.  23).  Place  the 
sciatic  nerve  upon  the  electrodes.  Moisten  the  preparation  repeatedly 
with  normal  saline  to  prevent  its  drying.  Stimulate  it  first  with  the 
constant  and  then  with  the  interrupted  current.  Do  the  results  agree 
with  those  obtained  by  stimulating  your  tongue  or  finger? 

Hold  the  electrodes  firmly  against  the  body  of  the  gastrocnemius 
muscle.  Repeat  the  stimulation  with  the  same  strength  of  current 
and  compare  the  effects  of  stimulating  the  muscle  directly  and  indi- 
rectly through  its  nerve.  Which  is  the  more  irritable  tissue  of  the  two, 
as  betrayed  by  the  threshold  value  of  the  current  required  to  activate  it? 

9.  Myography. — The  registration  of  the  contraction  of  muscle  neces- 
sitates a  means  of  holding  the  muscle,  a  writing  lever,  and  a  surface 
upon  which  the  record  may  be  made.  The  wi'iting  lever  is  fastened  to 
the  stand  below  the  muscle  clamp.     The  tendo  achillis  of  the  gastroc- 


MUSCLE    AND    NEUVE 


33 


nemius  is  then  cut  across  and  tlic  muscle  peeled  off  from  the  bones  of 
the  leg.  Next  the  hitter  are  cut  across  near  the  knee-joint  and  dis- 
carded, together  with  the  foot.  A  thread  is  then  tied  around  the  end 
of  the  tendon  and  connected  with  the  writing  lever  near  its  center  of 
rotation.  Below  the  tendon  a  slight  weight  is  attached  which  is  pre- 
vented from  extending  the  muscle  l)y  an  after-loading  device.  The 
electrodes  are  adjusted  upon  the  uj)per  part  of  the  nms(;le  (Fig.  11). 

The  recording  surface  is  formed  by  a  sheet  of  glazed  paper  which 
has  been  firmly  attached  to  the  surface  of  the  cylinder  of  a  kymograph 
and  has  been  covered  with  a  thin  layer  of  soot.  The  smoking  of  the 
drum  is  accomplished  most  conveniently  })y  suspending  it  in  a  smoking 
rack.     The  drum  is  then  revolved  at  the  rate  of  about  once  in  every 


Fig.  11. — A  Method  Used  to  Register  Muscul.\r  Contr.\ction. 
St,  Stand  for  holding  of  clamp  C  and  writinp:  lover  WL.    The  muscle  M  is  attached  to 
the  lever  by  means  of  a  small  hook  and  string.    The  lever  carries  weight  W.    The  stimula- 
tion is  effected  through  the  electrodes,  5.    The  speed  of  the  kymograph  K  may  be  varied 
by  fan  F. 

second,  while  a  broad  gas  flame  is  held  directly  underneath  with  its 
outer  yellow  zone  barely  touching  the  paper.  Smoke  the  paper  from 
left  to  right,  remaining  in  the  same  place  until  an  even  brown  surface 
has  been  produced.  Never  cease  rotating  the  drum  while  the  flame  is 
directed  against  the  paper,  and  do  not  overheat  the  latter,  otherwise  a 
burned  gray  surface  will  be  obtained.  When  properly  smoked,  the 
paper  should  possess  a  velvety,  chocolate-brown  color  (Fig.  12). 

Replace  the  drum  upon  the  rotating  disk  of  the  kymograph.  Adjust 
the  writing  lever  with  the  least  possible  friction  upon  the  paper,  and 
take  care  that  it  writes  as  a  tangent  upon  a  sphere  and  in  a  straight 
vertical  line.  The  writing  lever  is  provided  with  an  after-loading  device 
consisting,  as  a  rule,  of  a  screw-support  by  means  of  which  the  lever 
3 


34 


ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 


may  be  kept  in  the  horizontal  position  without  putting  an  additional 
weight  upon  the  resting  muscle. 

Stimulate  the  muscle  successively  with  the  make  and  break  shocks 
of  a  constant  current,  moving  the  drum  each  time  by  hand  a  distance 
of  a  few  millimeters.  Repeat  with  single  induction  shocks  of  medium 
strength.  Allow  the  drum  to  revolve  first  slowly  and  then  more  rapidly, 
and  repeat  the  stimulations.  Obtain  intermediate  speeds  of  the  drum 
by  placing  fans  of  different  size  upon  the  pivot  of  the  starting  gear. 

Observe  the  changes  in  the  out- 
line of  the  myogram  as  the  speed 
is  increased. 

Fasten  a  tuning-fork,  vibrat- 
ing one  hundred  times  in  a  second, 
to  a  separate  stand,  and  allow  its 
beats  to  be  registered  below  the 


"  L^n 


Fig.  12. — Arrangement  for  Smoking  the 
Paper.    {Univ.  of  Penna.  Lab.  Outlines.) 


myogram. 

Stimulate  the  muscle  with  a 
quickly  interrupted  current  (posts 
1  and  3)  for  a  period  of  five 
seconds,  and  record  its  contrac- 
tion upon  a  slowly  revolving 
drum.  Never  permit  the  tracing 
to  extend  across  the  line  where 
the  paper  has  been  glued  together. 

10.  Fixation  of  the  Records. — Write  your  name  upon  the  paper  and 
label  the  different  tracings.  Remove  the  drum  from  the  stand,  and 
hold  it  in  your  left  hand  with  the  tip  of  the  thumb  upon  the  edge  of  the 
paper.  Insert  the  tip  of  a  small  forceps  underneath  the  paper  near 
the  line  where  its  ends  have  been  glued  together.  Break  the  paper 
in  a  straight  line.  Hold  the  paper  firmly  between  your  hands  and 
draw  it  with  the  blackened  surface  turned  upward  through  a  solution 
of  shellac  in  alcohol.  Suspend  the  paper  in  the  frame  provided  for  this 
purpose  and  allow  it  to  dry.  Cut  out  the  different  tracings  and  paste 
them  in  your  note-book  in  an  orderly  manner. 

11.  Isotonic  and  Isometric  Myograms. — If  a  muscle  is  made  to  con- 
tract against  a  writing  lever  and  a  slight  load,  a  very  small  portion  of 
its  energy  will  be  used  up  in  overcoming  this  resistance.  By  far  the 
greatest  amount  of  its  energy,  however,  will  be  set  free  to  yield  visible 
mechanical  energy,  heat,  and  a  small  fraction  of  electricity.  If  the 
muscle  is  now  attached  near  the  fulcrum  of  the  lever,  while  the  end  near 
the  writing  point  is  prevented  from  moving  by  a  counter-force,  the 
shortening  of  its  fibers  will  be  i-educed  to  a  minimum  and  practically  no 
mechanical  energy  will  be  liberated.  A  relatively  much  larger  amount 
of  the  total  energy  will  thereby  be  converted  into  heat.  The  former 
arrangement  is  characterized  as  isotonic  and  the  latter  as  isometric. 


LESSON  III 


MUSCLE   AND   NERVE   (Continued) 

IRRITABILITY,  CONDUCTIVITY.  AND  ELASTICITY  OF  MUSCLE.  THE 
POWER  OF  MUSCLE  TISSUE  IN  RELATION  TO  THE  CROSS-SECTION 
AND  ARRANGEMENT  OF  ITS  FIBERS 

1.  Independent  Irritability  of  Muscle. — Pith  a  frog  and  destroy  its 
brain  without  losing  any  blootl.  Immediately  close  the  opening  with 
the  pointed  end  of  a  match.  Make  a  median  in- 
cision along  the  posterior  surface  of  the  left  thigh. 
Isolate  the  sciatic  nerve  carefuUj^  without  injur- 
ing the  femoral  vessels.  Tie  a  ligature  around  the 
thigh,  exclusive  of  the  sciatic  nerve.  With  a  large 
hypodermic  needle  inject  a  few  drops  of  curare 
under  the  skin  of  the  back.  Be  sure  that  the  solu- 
tion does  not  escape  through  the  incision  in  the 
thigh. 

After  its  absorption  the  curare  circulates  and 
is  carried  to  all  the  tissues  except  those  of  the  ligated 
leg.  When  a  complete  motor  paral\"sis  has  been  es- 
tablished in  about  fifteen  to  twenty  minutes  ex- 
pose both  sciatic  nerves  and  place  them  in  loose 
ligatures.  Also  expose  both  gastrocnemii  muscles 
by  cutting  an  oval  window  in  the  skin  over  each. 
Use  weak  induction  shocks  and  stimulate  the  sciatic 
nerve  on  the  side  of  the  ligature  (1)  as  well  as  on 
the  normal  side  (2),  In  the  same  way  stimulate 
both  gastrocnemii  muscles  (3  and  4).  The  follow- 
ing results  will  be  obtained:  (1)  positive,  (2)  nega- 
tive, (3)  positive,  (4)  positive. 


Annotation. — A  piece  of  solid  curare  (wurare  or  urare) 
is  pulverized  in  a  mortar  and  extracted  with  a  solution  of 
0.7  per  cent,  sodium  chlorid  until  dark  in  color.  Its  strength 
cannot  be  standardized,  but  must  be  determined  by  the 
physiologic  result.     Do  not  filter,  but  inject  as  it  is. 

Test  the  current  by  applying  the  electrodes  directly 
to  the  gastrocnemius  muscle.  Use  a  strength  of  ciu"rent 
just  sufficient  to  cause  a  well-marked  contraction.  If  a 
strong  current  is  used,  the  paralysis  must  be  more  com- 
plete, which  rcfjuires  a  larger  amount  of  curare. 

Curare  paralyzes  the  motor  plates  in  the  muscle,  and  hence  muscle  (4)  cannot 
be  activated  tlirough  its  nerve,  while  muscle  (3)  can  be.  Both  sciatic  nerves  conduct 
normally,  as  can  be  shown  Ijy  attacliing  the  poles  of  a  galvanometer  to  them.  In 
fact,  in  many  instances  tlie  stimulation  of  the  nerve  on  the  normal  side  (4)  jjroduces 
a  contraction  of  the  gastrocnemius  on  the  side  of  the  ligature.     The  elicitation  of 

35 


iTY  OF  Muscle. 

A ,  Dorsal  lymph 
sac  into  which  curare 
is  injected;  L,  liga- 
ture upon  left  thigh. 
The  stimulation  of 
the  sciatic  nerve  at  1 
is  then  effective,  but  is 
ineffective  at  2.  The 
gastrocnemii  muscles, 
when  stimulated  di- 
rectly at  3  and  4, 
give  a  contraction. 


36 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


this  reflex  proves  that  the  impulses  set  up  in  nerve  2  are  conveyed  into  the  spinal 
cord  and  from  here  outward  to  the  muscles  of  the  non-curarized  left  leg.  On  stim- 
ulating either  gastrocnemius  muscle  (3  and  4)  a  reaction  is  obtained.  This  proves 
that  the  curare  establishes  a  block  between  the  lierve-fibers  and  the  substance  of  the 
muscle,  /.  c,  it  paralyzes  the  motor  plates.  Secondly,  it  may  be  concluded  that  a 
muscle  which  has  been  isolated  in  this  manner  from  the  central  nervous  system  is 
still  irritable  and  contractile.  Consequently,  muscle  substance  so  isolated  is  capable 
of  acting  independently  of  the  nervous  tissue. 


2.  Irritability  and  Conductivity. — In  order  to  distinguish  between 
these  two  properties  of  living  substance  we  usually  make  use  of  a  nerve- 
muscle  preparation  which  is  placed  upon  a  plate, 
while  its  nerve  is  drawn  through  the  openings  of  a 
small  gas  chamber.  Pieces  of  moistened  filter-paper 
are  placed  flat  across  these  openings.  Inside  the 
chamber  the  nerve  rests  upon  a  pair  of  needle  elec- 
trodes {A),  and  outside  the  chamber  upon  a  pair  of 
ordinary  platinum  electrodes  {B).  Both  pair  of  elec- 
trodes are  connected  with  the  end-cups  of  a  pole 
changer.  The  side  cups  of  the  latter  are  then  united 
with  the  secondary  coil  of  an  inductorium.  The  inlet 
tube  of  the  gas  chamber  is  made  to  communicate 
with  a  generator  bottle  containing  pieces  of  marble. 

Stimulate  successively  at  A  and  B  with  induction 
shocks  of  moderate  strength.  A  positive  result  will 
be  obtained  in  each  case  provided  the  nerve  has  not 
been  injured.  Pour  a  small  quantity  of  20  per  cent. 
HCl  upon  the  marble.  Repeat  the  stimulations  as 
soon  as  the  CO2  has  begun  to  pass  over  into  the 
chamber.  It  will  be  found  that  the  stimulation  at 
A  is  now  less  effective  than  before  or  abolished  altogether.  Disconnect 
the  generator  and  blow  fresh  air  into  the  chamber.  Stimulate  again. 
Both  excitations  now  give  positive  results. 


Fig.  14.— Gas 
Chamber  for  De- 
termining THE  Ir- 
ritability AND 
Conductivity  of 
Nerve.  {Harvard 
Apparatus  Co.) 


Annotation. — The  carbon  dioxid  destroys  first  the  irritability  and  later  on  also 
the  conductivity.  As  this  gas  enters  the  chamber  containing  the  nerve  it  diminishes 
the  irritability  of  the  latter  (^1),  but  permits  its  conductivity  to  remain  practically 
normal  (5).     Consequently,  these  properties  of  nerve  are  independent  of  one  another. 


Pour  a  few  drops  of  alcohol  through  the  inlet  tube  of  the  gas  chamber, 
but  in  such  a  way  that  it  does  not  come  in  contact  with  the  nerve. 
Stimulate  at  A  as  well  as  at  B.  It  is  to  be  noted  that  the  stimulation 
at  B  now  remains  ineffective,  because  the  vapors  of  alcohol  have  de- 
stroyed the  conductile  power  of  the  nerve-fibers,  while  they  have 
diminished  their  irrital^ility  in  a  much  slighter  degree. 

3.  Extensibility  of  Muscle. — Use  the  same  preparation;  cut  off  the 
nerve  near  the  muscle,  and  fasten  the  femur  in  the  clamp.  Attach  the 
tendo  achillis  to  the  writing  lever  and  adjust  a  large  scale  pan  under- 
neath the  tendon.     Release  the  after-loading  appliance  so  that  the 


MUSCLE    AND    NERVE 


37 


Icvor  may  record  down-strokes.  Record  the  zero  lino  oi-  abscissa.  Put 
ten  weifjhts  of  10  firanis  each  successively  into  the  scale  pan,  recording 
each  time  the  extension  which  the  nuisde  suffers.  Carefully  I'cmove  the 
weights  one  by  one,  allowing  the  muscle  to  register  its  curve  of  deten- 
tion.    Does  thp  lever  return  to  the  abscissa? 

Obtain  a  curve  of  elasticity  from  a  rubber  band  under  similar  con- 
ditions. Coqipare  the  results.  Adjust  the  stimulating  electrodes  upon 
the  upper  part  of  the  nmscle.  Obtain  a  curve  of  elasticity  from  this 
muscle  while  it  is  being  stimulated  with  a  tetanic  current  of  moderate 
strength.  What  differences  do  you  detect  i)etween  this  curve  and  that 
obtained  under  ordinary  conditions?     Explain. 


JLOK 


/ 


Fig.  15. — Extensibility  and  Elasticity. 
A,  Rubber  band,  and  B,  Ktistrooncmius  muscle  of  frog  successively  loaded  with  10- 
grani  weights.     The  st>cond  curve  shows  a  decreasing  extension  for  equal  increments, 
hence,  the  line  joining  the  ends  of  the  ordinates  is  curved. 

Annotation. — A  rubber  band  is  perfectly  elastic,  ?'.  f.,  it  recoils  until  its  abscissa 
has  been  reached,  ]irovi(ied  it  has  not  been  extended  unduly.  The  same  holds  true 
of  muscles  in  .situ;  in  fact,  they  are  well  protected  against  all  excessive  degrees  of 
extension.  Outside  the  body  muscles  are  imperfectly  elastic.  After  their  con- 
stituent fibers  have  been  stretched  they  cannot  resume  their  original  shape.  A 
fatigued  muscle  (tetanized)  can  be  extended  much  more  easily  and  recoils  with  much 
greater  difficulty. 


4.  Measurement  of  Muscular  Power. — Prepare  a  gastrocnemius 
muscle  of  a  recently  killed  frog  and  fasten  the  femur  in  the  clamp. 
Connect  its  tendon  with  the  writing  lever.  Adjust  the  after-loading 
mechanism  so  that  the  lever  remains  horizontal.  Attach  weights  of 
100  grams  each  to  the  lever  until  the  muscle  is  no  longer  able  to  hft 
them  when  stimulated  with  a  tetanic  current  of  moderate  strength  and 
brief  duration.  Determine  the  maximal  load  lifted  and  also  the  weight 
of  the  muscle.     Compute  the  power  per  gram  of  muscle  substance. 

5.  Comparison  Between  Compact  and  Long  Muscles. — Prepare  the 
sartorius  muscle  of  the  opposite  leg  of  the  same  frog.  It  is  situated  upon 
the  inner  aspect  of  the  thigh  and  extends  between  the  ilium  and  the 
tibia.  Raise  its  tendon  at  the  tibia  and  tie  a  fine  silk  thread  around  it. 
Separate  the  entire  muscle  from  the  fascia  connecting  it  with  other 
muscles  and  cut  its  other  end,  leaving  the  ilium  attached.  Determine 
the  maximal  load  which  this  muscle  is  capable  of  lifting  under  condi- 
tions  identical  with    those    just    described.     Which   muscle  develops 


38 


ADVANCED    LESSONS   IN   PRACTICAL   PHYSIOLOGY 


more  power,  the  long  or  the  short  and  compact? 
does  the  latter  possess  over  the  former? 


What  advantage 


Annotation. — Short  compact  muscles,  such  as  the  gastrocnemius,  are  meant  to 
lift  hea\y  weights,  while  long,  slender  muscles,  such  as  the  sartorius,  excel  in  height 
of  contraction  rather  than  in  actual  force. 

6.  Relation  of  Force  to  Cross-section. — Prepare  the  other  gastroc- 
nemius muscle  of  the  same  animal.  Fasten  the  one  already  used  and 
this  one  side  by  side  in  the  clamp  and  connect  their  tendons  jointly 
with  the  writing  lever.  Determine  the  maximal  load  lifted  by  them 
in  the  manner  described  previously.  Quickly  disconnect  and  arrange 
these  muscles  tandem  by  uniting  the  tendon  of  one  to  the  point  of  at- 
tachment of  the  other  by  means  of  a  short  wire.     Adjust  one  wire  from 


'J 

;m 

;l:(|(iill(l 

llllhliiill 

=l# 

k' 

—            •         <     W 

~\  u 

~        %        1 1(  / ^ "" 

'^W' 

»-  )[-  - 

w 


F 


I    ^ 


w 


Fig.  16. — Schema  to  Show  that 
Contracting  Muscle  Does  Not 
Change  its  Volume. 

M,  Meniscus  of  saline  solution; 
iS,  electrodes  through  which  muscle 
in  receptacle  is  stimulated. 


I^ 


W 


Fig.  17. — Different  Systems  of  Levers. 
F,  Fulcrum;  P,  power;  W,  weight. 


the  secondary  coil  of  the  inductorium  to  the  body  of  the  upper  muscle 
and  the  other  to  the  body  of  the  lower  muscle.  Stimulate  with  the 
same  strength  of  current  used  before,  and  determine  the  maximal  load 
lifted  by  them  when  arranged  in  this  way  instead  of  side  by  side. 

7.  Effect  of  Contraction  Upon  the  Volume  of  the  Muscle. — Place 
one  of  these  gastrocnemii  muscles  in  the  glass  receptacle  provided  for 
this  purpose.  Be  sure  that  its  ends  are  firmly  attached  to  the  hooks 
projecting  from  the  bottom  and  top  of  this  receptacle.  Fill  the  recepta- 
cle with  boiled  saline  solution;  close  it,  and  adjust  the  capillary  tube  so 
that  the  "meniscus,"  indicating  the  level  of  the  liquid,  can  be  clearly 
seen.  Connect  the  ends  of  the  hooks  with  the  secondary  coil  of  an 
inductorium.  Stimulate  with  single  induction  shocks,  and  note  whether 
or  no  a  decided  change  results  in  the  position  of  the  meniscus  when  the 
muscle  contracts  (Fig.  16). 


MUSCLE    AND    NERVE  39 

Annotation. — Since  tlic  coiitractiiiK  iiiusclt'  does  not  iiitereliaiijje  material  with 
the  inediuin,  but  nierely  sliifts  its  substance,  its  volume  is  not  altered.  The  men- 
iscus remains  stationary,  provided  all  the  air  has  been  driven  out  of  the  saline  by 
boiling. 

8.  Manner  of  Attachment  of  the  Muscles  to  the  Bones. — DcternHiie 
the  position  of  tiie  t'lilciuin,  \v(M}i;ht  and  power  in  tli(>  cases  of  the  biceps 
in  fiexing  the  forearm,  ti'iceps  in  extending  the  forearm,  muscles  upon  the 
ventral  aspect  of  the  neck  in  moving  the  head,  gastrocnemius  in  raising 
the  body  on  tiptoe,  tibialis  anticus  in  raising  the  body  on  the  heel,  and 
the  masseter  in  raising  the  jaw  (Fig.  17). 

9.  Center  of  Gravity.— W it  li  chalk  outline  the  feet  of  a  person  when 
standing  erect.  Aijproximatel}'  determine  by  means  of  a  ruler,  held 
vertical,  the  position  of  his  center  of  gravity.  Attach  a  heavy  load  first 
to  the  front  and  then  to  the  back  of  his  body,  and  note  the  manner  and 
degree  in  which  the  body  is  shifted  to  support  the  center  of  gravity. 
What  use  may  l)e  made  of  the  legs  and  arms  in  gaining  additional  sup- 
port? Draw  a  diagram  illustrating  the  progression  of  the  center  of 
gravity  during  the  act  of  walking. 


LESSON  IV 

..     MUSCLE  AND   NERVE   (Continued) 

SINGLE  CONTRACTION,  SUMMATION  AND  FUSION  OF  CONTRACTIONS. 
TETANUS.  INFLUENCE  OF  CHANGES  IN  THE  STRENGTH  OF  THE 
STIMULUS  AND  LOAD  OF  THE  MUSCLE 

1.  Single  Contraction  or  "Twitch." — Attach  a  gastrocnemius  muscle 
to  the  clamp  and  the  writing  lever.  Place  an  electromagnetic  signal 
directly  below  the  writing  lever,  so  that  their  points  come  to  lie  close 
together  and  precisely  in  the  same  vertical  line  (ordinate).  Fasten  a 
scale  pan  underneath  the  writing  lever,  but  in  such  a  way  that  it  cannot 
interfere  with  the  movement  of  the  lever.  Connect  the  signal  in  series 
with  the  cells  and  posts  1  and  2  of  the  inductorium.  Adjust  the  sec- 
ondary coil  to  obtain  induction  shocks  of  medium  strength.  Fasten  a 
tuning-fork  to  a  separate  stand  which  is  placed  to  the  left  of  the  kymo- 
graph, so  that  the  pointer  of  the  fork  vibrates  against  the  rotation  of 


Fig.   18. — Electromagnetic  Signal.     (Univ.  of  Pcnna.  Lah.  Oullines.) 

the  drum.     Raise  the  drum  of  the  kymograph  from  its  friction-surface 
l)y  properly  adjusting  the  screw  in  the  top  of  the  rod. 

Let  the  tuning-fork  register  its  vibrations  (y^o  sec.)  directly  below 
the  record  of  the  signal.  With  your  left  hand  then  spin  the  drum  once 
around  its  axis,  and  with  your  right  hand  close  and  open  the  key  of 
the  primary  circuit.  The  speed  of  the  drum  should  be  such  that  the 
circuit  may  be  made  and  broken  conveniently  during  a  single  rotation 
of  the  drum.  Repeat  this  experiment  a  number  of  times.  Place  a 
ruler  vertically  against  the  kymograph  and  draw  perpendiculars  through 
the: 

41 


42 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


(a)  Moment  of  stimulation  as  indicated  by  the  signal, 
(6)  Point  at  which  the  muscle  just  begins  to  shorten, 

(c)  Point  at  which  the  muscle  shows  its  greatest  degree  of  short- 
ening, and 

(d)  Point  at  which  the  writing  lever  again  reaches  the  abscissa. 


Fig.  19. — A  Muscle  Twitch. 

M,  Make   shock  recorded  by  magnetic  signal  connected  with  primary  circuit.    Time  in 

xJij  sec;  L,  latent  period;  C,  period  of  contraction;  R,  period  of  relaxation. 

Determine  the  duration  of:  (a)  The  latent  period,  (6)  the  period 
of  contraction,  and  (c)  the  period  of  relaxation.  Note  that  the  muscle 
does  not  relax  properly  if  the  stimulus  is  too  strong,  and  that  the  length 
of  the  curve  increases  after  a  time,  owing  to  fatigue. 

2.  Summation  of  Contractions. — Remove  the  tuning-fork.  Use  a 
rapid  speed  of  drum  and  again  stimulate  the  muscle  with  a  make  and 


Fig.  20. — Summation  of  Contractions. 
M  and  B,  Make  and  break  shocks  indicated  by  an  electromagnetic  signal.     Time 
ui  i^Tj  sec.    As  the  break  contraction  occurs  during  the  period  of  relaxation  of  the  make 
contraction,  it  is  added  to  the  first. 

break  shock,  but  in  such  a  manner  that  the  break  stimulus  strikes  the 
muscle  during  its  period  of  relaxation.  A  second  contraction  then  re- 
sults which  is  added  to  the  first,  thereby  rendering  it  higher  than  the 
first. 

3.  Fusion  of  Contractions.^Reduce  the  speed  of  the  drum.  Repeat 
the  previous  experiment,  gradually  increasing  the  rate  of  stimulation 
until  the  contractions  resulting  from  the  separate  stimuli  are  partially 


MUSCLE    AND    NERVE  43 

and  completely  fused.     This  fusion  of  single  contractions  eventually 
gives  rise  to  a  tetanus. 

4.  Compound  Contraction  or  "Tetanus."— Connect  in  series  two 
dry  cells,  a  simple  key,  and  posts  1  and  3  of  the  inductorium.  Change 
the  gears  of  the  kymograph  so  as  to  obtain  the  slowest  possible  speed 
of  rotation.     Use  a  moderate  strength  of  current  and  stinuilate  the 


Fig.  21. — Fusion  and  Tet.\nus. 

5,   Summation;   F,   fusion;    T,  tetanus.      Time  in   seconds.      The   individual  make   and 

break  shocks  are  repeated  so  quickly  that  a  continuous  contraction  is  obtained. 

muscle  during  a  period  of  ten  seconds.  Compare  this  curve  with  the 
one  obtained  previously.  Since  the  tetanic  contraction  is  the  result  of 
the  summation  and  fusion  of  simple  twitches,  it  is  much  higher  and 
longer  than  a  twitch.  If  long  continued,  the  height  of  the  curve  de- 
clines slowly,  owing  to  fatigue. 


Fig.  22. — Tetanic  Contraction. 
Recorded  by  means  of  Neef's  automatic  interrupter.     Time   in  seconds.     The  decline 
of  the  curve  is  an  indication  of  fatigue. 

5.  Relation  of  the  Strength  of  Stunulus  to  the  Height  of  Contraction. 

— Prepare  a  gastrocnemius  muscle  and  fasten  the  femur  in  the  clamp. 
Connect  the  tendon  with  the  writing  lever,  and  put  a  10-gram  weight 
into  the  scale  pan.  Record  the  abscissa.  Retain  the  writing  lever  in 
this  line  by  means  of  the  after-loading  screw.  Apply  the  electrodes 
firmly  to  the  upper  part  of  the  muscle.  Push  the  secondary  coil  of  the 
inductorium  over  the  primary.     Record  the  make  contraction,  keeping 


44  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

the  fingers  of  your  right  hand  firmly  upon  the  key.  When  the  lever 
has  again  assumed  the  horizontal  position,  turn  the  drum  with  your 
left  hand  about  2  mm.  to  the  left,  and  record  the  break  contraction. 
Move  the  secondary  coil  outward  for  a  distance  of  1  cm.  Turn  the 
drum  5  mm.  to  the  left.  Again  make  and  break  the  current  as  described. 
Repeat  this  experiment,  constantly  increasing  the  distance  between  the 
coils,  1  cm.  at  a  time,  until  the  stimuli  cease  being  effective.  In  closing 
and  opening  the  key,  hold  the  handle  firmly,  so  that  a  steady  contact 
is  obtained  each  time.  Determine  the  threshold  values  of  the  make 
and  break  shocks  in  terms  of  "distance  of  coils"  and  "deviation  of  the 
secondary  coil."  Note  that  the  maximal  reactions  are  obtained  at 
about  1  or  2  cm.  distance  of  coils,  and  not  when  the  coils  are  fully 
approximated.  Beginning  at  this  point  the  height  of  the  contractions 
decreases  gradually  to  zero,  the  make  contractions  disappearing  sooner 
than  the  break  contractions.  Explain  this  difference  upon  the  basis 
of  the  results  of  Lesson  II. 


jLl 


in 


I        2,       3       t        S"      6       7       8      9       to       II       /£,      »5       I'^      '5 


FiG.  23. — Successive  Make  and  Break  Contractions. 
The  strength  of  the  current  is  gradually  diminished  by  more  widely  separating  the 
secondary  from  the  primary  coil.     The  figures  indicate  this  separation  in  centimeters 
of  distance.   M,  Threshold  of  make;  B,  threshold  of  break. 

6.  Summation  of  Subminimal  Stimuli. — With  induction  shocks 
which  just  fail  to  evoke  a  visible  contraction,  stimulate  the  muscle  at 
intervals  of  one  second.  Repeat  the  stimulation  at  a  much  faster  rate. 
Do  the  subminimal  stimuli  eventually  become  supraminimal? 

Annotation. — Two  \aews  may  be  held,  namely:  (a)  that  the  individual  electric 
potentials  are  added  to  one  another  and  finally  produce  a  potential  of  sufficient 
magnitude  to  stimulate,  and  (h)  that  the  successive  subminimal  stimuli  progressively 
increase  the  irritability  of  the  muscle  tissue  until  it  eventually  reacts  to  a  stimulus 
which,  when  applied  singly,  does  not  activate  it.  The  first  view,  therefore,  advo- 
cates a  summation  of  stimuli,  and  the  second,  a  summation  of  protoplasmic  exci- 
tability. 

7.  Relation  of  the  Amount  of  the  Load  to  the  Height  of  Contrac- 
tion.— Prepare  a  fresh  muscle  and  arrange  the  apparatus  for  stimulation 
with  moderate  break  shocks.  Attach  a  scale  pan  to  the  writing  lever  and 
record  the  abscissa.  Keep  the  lever  in  this  line  by  means  of  the  after- 
loading  device.  Record  a  make  and  break  contraction  upon  the  stationary 
drum.  In  this  case  it  is  permissible  to  record  both  in  the  same  ordi- 
nate, because  the  break  contraction  is  higher  than  the  make  contrac- 
tion, but  do  not  break  the  circuit  too  soon  after  the  make,  otherwise 


MUSCLE    AND    NERVE 


45 


you  will  ol)tain  ;i  simiinalioii.  Load  the  muscle  with  a  weight  of  10 
grams,  and  move  the  (hum  a  distance  of  about  o  mm.  to  the  left.  Re- 
peat the  stinuilation.     Continue  to  load  the  nmscle  successively  with 


O     to    zo    io  W   SO    to   •)o    80   90  /oo 

Fig.  24. — Influence  of  Load. 

This  muscle  has  been  successively  loaded  with  lO-grain  weights. 

10-gram  weights  until  it  ceases  to  show  an  appreciable  contraction. 
Observe  the  general  outline  of  the  curve  obtained,  and  formulate  a 
general  rule  regarding  the  height  of  the  contraction  and  the  load. 


Fig.  25. — Diagram  of  Work-adder. 

A,  Wheel  which  is  turned  by  muscle  M  in  direction  of  arrows.     It  i?'  held  in  place  by 

brake  B.     Each  contraction  of  muscle  raises  weight  W. 

8.  Muscular  Work. — Obtain  in  millimeters  the  values  for:  L,  the 
total  length  of  the  wiiting  lever,  /,  the  distance  from  its  axis  to  the 
point  of  attachment  of  the  muscle,  and  H,  the  height  of  each  contraction. 

In  accordance  with  the  formula,  L  :  H  ::  I  :  h,  compute  the  height 
to  which  the  weight  has  been  lifted  during  each  contraction  (h).     The 


46  ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 

work  (W)  performed  by  the  muscle  each  time  equals  the  weight  (w) 
multiplied  by  the  height  to  which  it  has  been  lifted  (h).  The  work  of 
the  muscle  is  expressed  in  gram-millimeters. 

9.  Addition  of  Work.^ — In  order  to  determine  the  amount  of  work 
accomplished  by  a  muscle  in  a  given  period  of  time  we  make  use  of  an 
instrument  which  is  known  as  a  work-adder  (Fick).  Adjust  this 
instrument  upon  the  edge  of  the  table,  allowing  the  weight  (10  grams) 
suspended  from  its  pulley  to  touch  the  floor.  Fasten  the  femur  of  a 
gastrocnemius  preparation  in  the  clamp  and  attach  its  tendon  to  the 
lever  of  the  work-adder.  Apply  the  electrodes  to  the  upper  part  of 
the  muscle,  and  stimulate  it  at  the  rate  of  once  in  every  second  during 
a  period  of  thirty  seconds.  The  individual  make  and  break  shocks 
may  be  put  in  successively,  i.  e.,  it  is  not  necessary  to  short-circuit  the 
makes.  Compute  the  work  performed  during  this  period  by  multi- 
plying the  weight  by  the  height  to  which  it  has  been  lifted  (W  =  wh). 

Annotation. — In  short-circuiting  the  make,  the  cross-bar  attached  to  the  rods 
of  the  secondary  coil  is  moved  downward  into  its  position  of  closure.  The  current 
is  then  made,  but  cannot  reach  the  muscle  because  it  selects  the  route  of  least  re- 
sistance across  the  bar.  Now  open  this  bridge  and  break  the  circuit.  The  break 
shock  may  be  short-circuited  by  simply  closing  the  bridge  directly  after  the  make 
has  been  allowed  to  enter  the  muscle. 


LESSON  V 

MUSCLE  AND  NERVE  (Continued) 

INFLUENCE  OF  TEMPERATURE.  CHEMICALS.  AND  FATIGUE  UPON  THE 
CONTRACTION  OF  MUSCLE 

1.  The  Influence  of  Changes  in  Temperature  on  Contraction.— Fill 
the  outer  space  of  the  muscle  chanil^er  with  cracked  ice  and  fasten  it  in 
the  stand.  Suspend  a  gastrocnemius  muscle  from  the  hook  upon  the 
inner  surface  of  its  cover  and  connect  the  tendo  achillis  by  means  of  a 
long  thread  with  a  writing  lever  placed  directly  underneath  the  floor  of 


Fig.  26. — The  Musci^e  Warmer. 
An  apparatus    for    studying    the    influence  of   temperature    on    muscular    contraction. 

{Porter.) 

the  chamber.  Fasten  the  ends  of  the  wires  from  the  secondary  coil  in 
the  upper  part  of  the  muscle,  and  arrange  the  inductorium  for  stimula- 
tion with  single  induction  shocks.  Suspend  a  thermometer  next  to  the 
muscle  in  the  inner  compartment,  but  in  such  a  way  that  its  bulb  does 
not  come  in  contact  with  the  metal. 

When  the  temperature  has  reached  a  point  near  zero,  record  a  single 
break  contraction  upon  a  rapidly  revolving  drum.     Be  sure  to  break 

47 


48  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

directly  behind  the  hne  where  the  edges  of  the  paper  have  been  ghied 
together.  Without  removing  the  writing  lever  from  the  drum,  revolve 
the  latter  to  this  line.  By  means  of  an  alcohol  lamp  gradually  raise 
the  temperature  in  the  muscle  chamber  to  5°  C.  Make  the  current. 
Allow  the  drum  to  revolve,  and  when  the  writing  lever  has  passed  the 
first  contraction,  open  the  circuit.  Again  rotate  the  drum  to  the 
aforesaid  Hne;  adjust  the  writing  lever  in  the  abscissa,  and  heat  to 
10°  C.  Make  the  current  and  allow  the  drum  to  revolve,  again  break- 
ing the  circuit  directly  after  the  second  contraction.  Repeat  this  pro- 
cedure at  intervals  of  5  degrees  up  to  40°  C.  Contrast  the  sluggish 
contractions  obtained  at  low  temperatures  with  the  rapid  twitches 
obtained  at  higher  temperatures.  Is  the  increase  in  the  height  and 
decrease  in  the  length  of  the  individual  contractions  uniform? 

Increase  the  temperature  still  further,  and  revolve  the  drum  by  hand 
a  Kttle  at  a  time.  At  about  43°  C.  the  frog's  gastrocnemius  enters  the 
state   of    heat-rigor,   and    finally   shortens   maximally.     Remove    the 


Fig.  27. — Effect  of  Changes  in  Temperature  on  Muscular  Contraction. 
The  temperature  was  raised  5  degrees  each  time. 

muscle  from  the  chamber  and  examine  its  texture  and  appearance. 
Stimulate  it  and  ascertain  whether  it  contracts. 

Annotation. — By  attaching  an  automatic  key  to  the  kymograph  the  cm-rent 
may  be  broken  precisely  at  the  same  moment.  This  permits  the  individual  con- 
tractions to  become  superimposed  (Fig.  27). 

2.  Influence  of  Chemicals  on  Contraction. — Inject  a  few  drops  of 
a  1  per  cent,  solution  of  veratrin  sulphate  into  the  dorsal  lymph-sac  of 
a  frog.  Wait  fifteen  minutes.  Prepare  the  gastrocnemius  muscle  in 
the  usual  manner,  and  fasten  the  femur  in  the  clamp.  Attach  its 
tendon  to  the  writing  lever,  and  arrange  the  inductorium  for  stimula- 
tion with  single  induction  shocks  of  moderate  strength.  Record  several 
contractions  upon  a  rapidly  revolving  drum.  Study  the  character  of 
the  contraction  of  the  veratrinized  muscle.  Wherein  does  it  differ 
from  the  contraction  of  normal  muscle?    Also  note  that  the  veratrin 


MUSCLE    AND    NERVE  49 

reactions  commonly  alternate  with  perfectly  normal  ones.     The  reason 
for  this  is  not  known.     Heat  neutralizes  the  influence  of  venitrin. 

Annotation. — In  order  to  ('conoinizx',  the  other  ^astrorneiiiius  niiisele  of  the 
frog  used  for  the  precedinj^  experniient  may  l)e  iininersed  for  a  few  moments  in  a 
1  i)er  rent,  sohitioii  of  veratrin.  If  it  is  then  adjusted  in  the  recording  apparatus,  it 
will  give  eharacteristic  veratrin  rontraetions. 


'Is'sic .  .  .  • 

Fig.  28. — The  Effect  of  Veratrin  on  Muscular  Contraction. 

3.  The  Effect  of  Excessive  Stimulation  on  Contraction.    Fatigue. — 

Attach  a  fresh  gastrocnemius  muscle  to  the  recording  apparatus.  Put 
a  10-gram  weight  in  the  scale  pan.  Ai-range  the  electric  apparatus  for 
stimulation  with  single  induction  shocks  of  moderate  strength.  Make 
the  current.  Allow  the  drum  to  revolve  at  a  rapid  rate  and  break  the 
current  after  the  writing  point  has  passed  the  line  where  the  papei-  has 
been  glued  together.  Turn  the  drum  by  hand  to  the  end  of  the  paper 
without  removing  the  writing  lever.  Now  stimulate  the  muscle  at  brief 
intervals  with  twenty-five  make  and  break  shocks.  After  the  twenty- 
sixth  make  contraction  hold  the  bridge  of  the  key  down.     Allow  the 


•r 


Fig.  29. — Fatigue  of  Muscle. 

A  gastrocnemius  muscle  of  the  frog  stimulated  successively  150  times.     The  1st,  aOth, 

100th,  and  150th  contractions  are  recorded. 

drum  to  revolve  and  record  the  twenty-sixth  break  contraction  directly 
after  the  first.  Again  stimulate  the  muscle  twenty-five  times  near  the 
Une  where  the  paper  has  been  pasted  together,  and  record  the  fifty- 
first  break  contraction  as  described.  Repeat  this  procedure,  recording 
the  contractions  at  these  intervals  until  the  muscle  ceases  to  lift  the 
lever.  Compare  the  different  curves  with  one  another,  noting  their 
relative  heights  and  lengths.  Wherein  does  fatigue  betray  itself?  Wait 
five  minutes  and  stimulate  the  muscle  again.  Does  it  regain  its  power 
of  contraction?  Compare  its  behavior  with  that  of  a  normal  muscle 
after  excessive  exercise. 


50  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

Annotation. — If  this  muscle  possesses  a  high  degree  of  irritabiUty,  increase  the 
number  of  the  contractions  between  the  successive  records.  Since  a  veiy  responsive 
muscle  may  contract  as  many  as  750  times  against  a  weight  of  20  grams  before  it 
is  fatigued,  the  differences  between  the  successive  contractions  might  not  be  suf- 
ficiently evident  unless  some  such  procedm-e  is  followed  to  hasten  the  onset  of  fatigue. 
Naturally,  fatigue  may  also  be  brought  on  more  quickly  by  increasing  the  weight 
lifted  by  the  muscle.  As  has  been  stated  above,  the  writing  lever  should  not  be 
removed  from  the  smoked  paper,  because  this  alters  the  friction  and  interferes  with 
the  steady  decline  and  lengthening  of  the  successive  curves. 

Use  the  other  gastrocnemius  muscle  of  the  same  frog  and  attach  it 
to  the  recording  apparatus.  Arrange  the  electric  apparatus  for  stimula- 
tion with  a  quickly  interrupted  current  (posts  1  and  3  of  the  induc- 
torium).  Upon  a  slowly  revolving  drum  record  a  tetanic  contraction 
lasting  twenty  seconds.  Directly  underneath  record  a  second  contrac- 
tion of  equal  duration,  and  underneath  this  one,  a  third  and  fourth, 
until  the  muscle  has  been  fatigued. ' 


LESSON  VI 

MUSCLE  AND  NERVE  (Continued) 

CONTRACTION  OF  HUMAN  MUSCLE.     INFLUENCE  OF  BLOOD-SUPPLY. 

SMOOTH  MUSCLE 

1.  Contraction  of  Human  Muscle. — Adjust  your  right  foroarin  in 
the  holder  of  the  crgogniph  and  place  the  middle  finger  in  the  sling 
supporting  a  weight  of  2  to  3  kilos.  Attach  a  pointer  to  the  latter, 
permit  ling  it  to  rest  against  the  paper  of  a  kymograph.  Make  several 
voluntary  contractions  upon  a  rapidly  revolving  drum  and  above  the 
record  of  a  tuning-fork.  Estimate  the  amount  of  work  accomplished 
each  time. 


Fig.  30. — Mosso's  Ergograph. 
C  is  the  carriage  moving  to  and  fro  on  runners  by  means  of  the  cord  d,  which  passes 
from  the  carriage  to  a  holder  attached  to  the  hast  two  phalanges  of  the  middle  finger 
(the  adjoining  fingers  are  held  in  place  by  clamps);  p,  the  writing  point  of  the  carriage, 
c,  which  makes  the  record  of  its  movements  on  the  kymographion;  w,  the  weight  to  be 
lifted.     {Howell.) 

Use  a  very  slow  drum.  Flex  the  middle  finger  and  retain  it  in  this 
position  until  the  end  of  the  paper  has  been  reached  (tetanic  contrac- 
tion).    Note  the  oscillations  and  resulting  fatigue. 

Use  a  very  slow  drum.  Flex  the  middle  finger  at  a  definite  rate, 
say,  once  in  every  second,  until  fatigue  has  resulted.  Allow  the  speed 
of  rotation  to  be  indicated  by  a  chronograph  beating  at  intervals  of  two 
seconds. 

Annototion. — If  Mosso's  ergograph  is  not  available,  use  a  spring  ergograph  which 
consists  of  a  horizontal  lever  attached  to  a  metal  upright.  The  fingers  of  the  right 
hand  are  securely  fastened  in  a  liolder,  while  the  index-finger  of  the  same  hand  is 
abducted  against  the  lever.     Isotonic  contractions  are  obtained  if  the  rod  resting 

51 


52 


ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 


upon  the  index-finger  and  connecting  the  latter  with  the  lever  is  moved  far  out 
toward  the  writing  point.  Isometric  effects  result  if  the  vertical  rod  is  adjusted 
near  the  metal  support  of  the  lever  (Fig.  31). 

2.  Dynamometer. — Place  a  dynamometer  in  your  right  hand  and 
contract  the  muscles  against  its  spring.  How  great  a  force  can  5^ou 
exert?     Repeat  with  the  left  hand.     Compare. 

3.  Ergographic  Record  of  the  Frog's  Gastrocnemius. — Procure  a 
metronome  and  insert  it  in  the  primary  circuit  of  the  inductorium. 
Adjust  it  to  yield  one  stimulus  in  every  second.  Pith  a  frog  and  pre- 
pare a  gastrocnemius  muscle.  Attach  it  to  the  writing  lever  in  the 
usual  manner.  Allow  the  drum  of  the  kymograph  to  revolve  at  a  slow 
rate,  and  register  the  successive  contractions  of  the  muscle  until  fatigue 


Fig.  31. — Speing  Ergogeaph.     (^Harvard  Apparatus  Co.) 


has  set  in.     How  many  contractions  have  been  obtained  and  during 
how  long  a  period? 

4.  The  Influence  of  the  Blood-supply  Upon  Muscular  Contraction. — 
Procure  a  metronome  and  insert  it  in  the  primary  circuit  of  the  induc- 
torium. Adjust  this  instrument  to  stimulate  once  in  every  second. 
Pith  a  frog  and  block  the  opening  with  a  pointed  piece  of  match  so  that 
no  blood  is  lost.  Fasten  the  frog  upon  a  narrow  board  of  cork  raised 
to  the  height  of  the  upper  margin  of  the  drum  of  the  kymograph. 
Isolate  the  femoral  blood-vessels  on  one  side  and  ligate  them.  Make  an 
incision  through  the  skin  of  the  ankle  and  separate  the  tendo  achillis 
from  the  bone.  Attach  a  silk  thread  to  the  tendon  and  connect  it  across 
a  pulley  wheel  with  a  writing  lever  adjusted  upon  the  paper  of  the 
kymograph  underneath  the  edge  of  the  cork  board.  Isolate  the  oppo- 
site tendo  achillis  in  the  same  way,  and  connect  it  with  a  second  writ- 


MUSCLE    AND    NERVE 


53 


ing  lever  phicetl  in  the  same  (jidiiuite  below  the  fiist.  I'ull  uixjii  the 
strings  to  ascertain  whether  these  levers  interfere  with  one  another. 
Attach  a  weight  of  10  grams  to  (>ach.  Make  a  small  opening  in  the  skin 
over  the  upper  part  of  each  gaslrociuMnius  muscle,  Fasten  the  wires 
from  the  secondary  coil  of  the  inductorium  near  the  knee-joint — one 
on  each  side.  Then  complete  the  circuit  by  uniting  the  gastrocneniii 
muscles  by  means  of  a  short  piece  of  flexible  wire. 

Allow  the  (h'um  <jf  the  kynwjgraph  to  revolvi;  very  slowly.  Record 
the  contractions  of  these  muscles  in  the  same  ordinate  until  completely 
fatigued.  Note  that  the  bloodless  muscle  is  much  niore  easily  fatigued. 
Explain. 

o.  Smooth  Muscle.^Connect  the  secondary  coil  of  the  induc- 
torium with  the  two  outside  posts  of  a  moist  chamber  and  attach  two 
shorter  wires  of  medium  thickness  to  the  corresponding  inside  posts. 


Fig.  32. — Moist  Chamber. 

S,  Stand;  M,  muscle;  E,  electrodes;  L,  writing  lever;  TM,  signal;   A',  simple  key;  PS, 

inductorium;  if',  short-circuiting  key.     (Stirling.) 

Place  a  piece  of  filter-paper  moistened  with  saline  solution  against  the 
inner  surface  of  the  glass  cover.  If  the  temperature  of  the  room  is 
low,  place  a  lighted  alcohol  lamp  at  some  distance  below  the  floor  of  the 
moist  chamber.  Arrange  the  electric  apparatus  for  stimulation  with 
single  induction  shocks. 

Obtain  a  preparation  of  smooth  muscle  tissue  and  fasten  it  in  the 
clamp  at  the  end  of  the  horizontal  rod  in  the  moist  chamber.  To  its 
other  end  tie  a  silk  thread,  which  is  then  brought  through  the  orifice  in 
the  floor  of  the  chamber  and  fastened  to  the  wi-iting  lever  directly 
underneath  the  latter.  The  writing  lever  should  be  adjusted  in  a 
horizontal  position  by  moving  it  up  or  down.  Do  not  tighten  the  after- 
loading  screw,  because  the  lever  should  at  first  be  able  to  move  upward 
as  well  as  downward.  Fasten  the  ends  of  the  short  wires  in  the  top  of 
the  preparation.     Adjust  a  chronograph  underneath  the  point  of  the 


54  ADVANCED    LESSONS   IN    PRACTICAL    PHYSIOLOGY 

\NTiting  lever.  Allow  it  to  register  at  intervals  of  two  seconds.  Allow 
the  drum  to  revolve  very  slowly  and  observe  whether  the  muscle  records 
spontaneous  contractions. 

Draw  the  abscissa,  and  adjust  the  writing  lever  properly  in  this  line. 
Start  at  the  beginning  of  the  paper  and  stimulate  the  muscle  with  a 
single  break  shock.  If  the  preparation  does  not  react  to  this  strength 
of  stimulus,  put  in  two  or  more  shocks  in  quick  succession — makes  and 
breaks,  if  j'ou  choose.  Note  the  unusual  length  of  the  latent  period. 
Allow  the  muscle  to  relax  fully,  which,  if  the  contraction  possesses  a 
height  of  about  5  cm.,  may  require  the  entii'e  length  of  the  paper. 

Produce  a  summation  of  contractions  by  stimulating  the  muscle  first 
by  means  of  a  make  shock  and  again  with  a  break  shock  very  shortly 
after  it  has  entered  upon  its  period  of  relaxation.  Naturally,  if  single 
stimuh  do  not  prove  effective,  employ  a  number  of  them  in  quick  suc- 
cession. 

Employ  a  brief  tetanic  current,  being  careful  not  to  contract  the 
muscle  excessively,  otherwise  it  might  not  be  able  to  complete  its  period 


Fig.  33. — Contraction  of  Smooth  Muscle  (Cat's  Bladder). 
L,  Latent  period;  C,  period  of  contraction;  R,  period  of  relaxation;  time  in  seconds. 

of  relaxation  before  the  end  of  the  paper  has  been  reached.  Does  the 
character  of  the  "tetanic"  curve  of  smooth  muscle  differ  from  that  of 
the  curve  obtained  with  single  stimuli? 

Annotation. — Preparations  of  smooth  muscle  may  be  obtained  most  conveni- 
ently from  the  stomach  of  the  frog  and  the  stomach,  intestine,  and  bladder  of  the 
cat.  No  doubt,  the  bladder  is  best  adapted  for  this  purpose.  Having  opened  the 
abdomen  in  deep  narcosis,  the  bladder  is  partially  emptied  and  lifted  out  of  the 
wound.  A  long  silk  thread  is  then  tied  around  the  urethra  at  a  distance  of  1  to  2 
cm.  from  the  cervLx  of  the  bladder.  The  upper  pole  of  the  fundus  is  securely  fastened 
to  a  pair  of  needle  electrodes  and  quickly  placed  in  the  moist  chamber  prepared 
as  described  above.  The  silk  thread  is  attached  to  the  writing  lever  placed  at  a 
convenient  distance  below  the  floor  of  the  chamber.  Do  not  injure  the  organ 
mechanically,  and  moisten  it  from  time  to  time  with  slightly  warmed  saline  solution. 

If  the  stomach  is  employed,  cut  a  ring  about  1  cm.  in  width  from  its  pyloric 
portion  and  fasten  it  in  this  position  to  the  rod  of  the  moist  chamber.  To  its  upper 
pole  attach  one  of  the  ^^^res  from  the  secondary  coil  of  the  inductorium.  To  its 
lower  pole  attach  the  wTiting  lever  by  means  of  a  thread  and  also  the  other  wire 
from  the  secondary  coil.  The  same  procedure  is  to  be  followed  in  the  case  of  seg- 
ments of  intestine.  Be  sure  not  to  arrange  them  horizontally,  because  only  \he 
circular  mu.sde-fibers  will  give  a  marked  movement  of  the  lever.  Under  proper 
conditions  of  experimentation  the  frog's  stomach  will  yield  contractions  2  to  3  cm. 
in  height. 


LESSON  VII 

MUSCLE  AND  NERVE  (Continued) 

SPEED  OF  THE  NERVE  IMPULSE  IN  THE  FROG  AND  MAN. 
TION  IN  BOTH  DIRECTIONS 


CONDUC- 


L  Histologic  Study  of  Nerve  Tissue. — Examine  nerve  tissue  under 
the  low  and  hij;h  jxjwers  of  a  inicroscopc.  Employ  horizontal  as  well 
as  transverse  sections.  Identify  the  axis-cylinder  with  its  fibrils,  the 
medullary  siioath,  neurilcinnia,  and  nodes  of  Hanvicr. 

2.  Speed  of  the  Nerve  Impulse  in  Cold-blooded  Animals. — Place 
two  pairs  of  needle  electrodes  upon  the  rod  in  the  moist  chamber,  and 
connect  them  by  means  of  wire  of  medium  caliber  with  their  cor- 
responding binding-posts  inside  the  chamber.     Attach  the  wires  from 


Fig.  34. — Speed  of  the  Nerve  Impulse. 
M,  Mui?cle  and  nerve  connected  with  writing  lever  W  and  two  pairs  of  electrodes 
-V  and  F.     The  wires  from  inductorium  ./  are  connected  with  the  pole  changer  P,  so  that 
the  nerve  may  be  stimulated  either  near  to  or  far  away  from  the  muscle. 

the  secondary  coil  of  the  inductorium  to  either  pair  of  outside  posts. 
Underneath  the  moist  cham])er  adjust  a  writing  lever  and  electromag- 
netic signal.  The  writing  point  of  the  latter  should  be  adjusted  in  the 
same  ordinate  as  the  point  of  the  recording  lever.  The  binding-posts 
upon  the  signal  are  connected,  on  the  one  hand,  with  post  1  of  the 
inductorium  and,  on  the  other,  with  the  simple  key.  From  the  latter 
the  wire  is  continued  onward  to  the  dry  cell  and  subsequently  to  post  2 
of  the  inductorium.  Adjust  the  secondary  coil  to  give  induction  shocks 
of  medium  strength. 

Make  a  muscle-nerve  preparation,  taking  care  not  to  injure  the  nerve. 
Permit  the  lower  segment  of  the  spinal  cord  to  remain  attached  to  it. 


56 


ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 


In  the  frog  the  cord  extends  as  far  as  the  ninth  vertebra  (at  the  dorsal 
prominence).  From  here  the  tenth  vertebra  or  urostyle  passes  back- 
ward to  the  tip  of  the  animal.  It  is  best  to  open  the  abdominal  cavity 
in  the  median  line  and  to  remove  the  viscera.  Make  two  transverse 
sections  so  as  to  isolate  the  seventh  and  eighth  vertebrae  and  roots  of 
the  sciatic  nerve  of  one  side.  Trace. these  fibers  through  the  pelvic 
aperture  and  down  upon  the  dorsal  aspect  of  the  thigh.  Isolate  the 
gastrocnemius  muscle  and  place  the  coiled  up  nerve  temporarily  upon 
it,  but  do  not  allow  it  to  come  in  contact  with  the  skin.  Remove  the 
muscles  of  the  thigh  and  cut  the  femur.  Adjust  this  preparation  in 
the  clamp  of  the  moist  chamber  and  lay  the  nerve  across  the  widely 
separated  needle  electrodes.  Moisten  the  nerve  with  saline  solution 
and  replace  the  glass  cover.  Test  the  two  electrodes  to  see  whether 
both  are  effective. 

The  procedure  to  be  followed  is  the  same  as  that  described  previously 
for  determining  the  different  periods  of  the  muscle  twitch.     Having  set 


Pohl's  Commutator.     (Univ.  of  Penna.  Lab.  Outlines.) 


the  tuning-fork  in  vibration,  the  muscle  is  made  to  contract  by  closing 
the  key,  the  contraction  may  occupy  a  single  rotation  of  the  drum, 
and  must  be  repeated  a  number  of  times  on  far  stimulation  as  weU  as 
on  near  stimulation.  Obviously,  the  current  may  be  diverted  into 
either  pair  of  electrodes  by  simply  changing  the  position  of  the  wires 
at  the  binding-posts  outside  the  moist  chamber.  A  pole  changer  may 
also  be  employed,  but  since  this  requires  considerable  lengths  of  extra 
wire  the  change  may  be  more  conveniently  effected  in  the  manner  sug- 
gested above. 

Draw  perpendiculars  to  determine  the  length  of  the  latent  period 
on  near  and  far  stimulation.  Measure  the  distance  between  the  elec- 
trodes in  millimeters.  The  time  occupied  by  the  nerve  impulse  in 
traversing  the  measured  stretch  of  nerve,  corresponds  to  the  difference 
in  the  latent  periods.     Calculate  the  velocity  of  the  nerve  impulse. 

3.  Rate  of  the  Nerve  Impulse  in  Man. — A  simple  method  for  deter- 
mining the  speed  of  the  nerve  impulse  in  man  not  being  available,  the 


MUSCLP]    AND    NERVE  57 

following  procedure  maj'  be  tried:  Connect  a  rubber  bull  by  means  of 
rubber  tubinji;  with  a  recording  tambour,  and  request  the  subject  to 
hold  the  ball  between  his  middle  finder  and  thumb.  Adjust  an  electro- 
magnetic signal  underneath  the  tanil)our  in  such  a  way  that  their 
writing  points  come  to  lie  in  the  same  ordinate.  Place  a  tuning-fork 
fastened  to  a  separate  stand  below  the  latter,  its  pointer  being  directed 
against  the  rotation  of  the  di'um.  The  binding-posts  of  the  signal  are 
then  connected  in  series  with  a  key,  posts  1  and  2  of  the  inductorium, 
and  a  dry  cell.  From  the  secoiulary  coil  two  wires  are  led  off  to  a  pair 
of  cUnical  electrodes.  The  large  indifferent  electrode  is  placed  upon  the 
outer  aspect  of  the  arm  of  the  subject,  whereas  the  pointed  one  is  held 
against  the  region  of  the  median  nerve  at  the  bend  of  the  elbow. 

Allow  the  tuning-fork  to  vibrate.  Spin  the  drum  with  your  left 
hand,  and  close  the  key  with  your  right  hand.  The  moment  of 
stimulation  will  be  recorded  by  the  signal,  and  the  moment  of  con- 
traction of  the  flexor  muscles  by  the  tambour.     Draw  ordinates  and 


Fig.  36. — Conduction  in  Both  Dikections  in  Gracilis  Muscle. 

A   and  B,  Segments  of  gracilis  muscle  divided  by  cut  (C);  S,  point  of  stimulation;  A'', 

motor  nerve  and  its  branches. 

determine  the  length  of  the  latent  period.  Repeat  this  experiment 
while  the  stimulating  electrode  is  held  over  the  brachial  nerves  above 
the  clavicle.  Again  determine  the  length  of  the  latent  period.  The 
difference  in  the  latency  between  the  two  contractions  corresponds  to 
the  time  consumed  by  the  impulse  in  its  passage  from  the  region  of 
the  clavicle  to  the  elbow.  Measure  this  distance,  and  calculate  from 
these  data  the  rate  of  transmission  of  the  nerve  impulse. 

4.  Nerve-fibers  may  be  Made  to  Conduct  in  Both  Directions. — 
Pith  a  frog  and  reflect  the  skin  from  the  ventral  surface  of  the  thigh. 
Cut  transversely  across  the  sartorius  muscle  near  the  knee  and  again 
near  the  ilium.  Isolate  the  muscle  along  its  outer  border  and  turn  its 
entire  mass  inward,  so  that  its  under  surface  is  brought  into  full  view. 
Its  nerve  will  be  seen  to  enter  near  the  middle  of  its  inner  border,  where 
it  divides,  sending  branches  toward  both  poles  of  the  muscle.  With 
the  scissors  cut  transversely  across  the  different  muscle-fibers  well  into 
the  triangle  formed  by  the  dividing  nerve,  so  as  to  destroy  the  con- 


58  ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 

tinuity  between  the  two  ends  of  the  muscle.  Beginning  at  one  end  of 
the  muscle,  cut  across  the  nerve  terminals  repeatedly,  noting  that  the 
fibers  in  the  other  end  of  the  muscle  then  contract.  Do  not  stimulate 
with  the  electrodes,  because  this  might  invite  the  criticism  that  the  con- 
traction of  the  distant  fibers  is  due  to  current  skipping.  The  neigh- 
boring graciUs  muscle  may  also  be  used  for  this  experiment. 

Annotation. — ^This  motor  nerve  conducts  ordinarily  in  a  centrifugal  direction. 
Since  the  stimulation  of  its  terminals  in  one  end  of  the  divided  muscle  also  gives 
rise  to  a  muscidar  response  in  the  other  end  of  the  muscle,  the  impulses  here  gener- 
ated must  be  conveyed  in  an  afferent  direction  to  the  nearest  divisions  of  these 
efferent  fibers,  whence  they  proceed  over  the  normally  efferent  fibers  to  the  other 
pole  of  the  muscle.  In  this  way  a  normally  efferent  fiber  may  be  made  to  conduct  in 
an  afferent  direction.  While  it  is  probable  that  this  nerve  contains  a  certain  number 
of  afferent  neurons,  their  presence  cannot  nullify  the  significance  of  this  experiment, 
because  in  the  e^•ent  of  their  activation  their  impulses  could  only  be  transferred  to 
the  other  end  of  the  muscle  by  changing  then-  normally  afferent  into  an  efferent 
type  of  conduction. 


LESSON  VIII 
MUSCLE  AND  NERVE    Continued) 

CONDUCTION  IN  NERVE.     ACTION  CURRENT  OF  MUSCLE  AND  NERVE. 
STIMULATION  OF  MOTOR  POINTS 

1.  Motor  Nerve  More  Irritable  Near  its  Center. — Pith  a  frog. 
Expose  the  sciatic  nerve  in  two  places,  namely:  (a)  in  the  pelvis  by 
an  incision  between  the  urostyle  and  the  ilium,  and  (b)  in  the  thigh 
(dorsal)  near  the  gastrocnemius  muscle.  Insulate  both  segments  care- 
fully by  means  of  narrow  strips  of  rubber  membrane.  Arrange  the 
electric  apparatus  for  stimulation  with  single  induction  shocks  and  de- 
termine the  least  strength  of  make  or  break  shocks  which  will  give  a 
contraction  in  these  two  places.     Compare  the  results. 

2.  Influence  of  Temperature. — Isolate  the  nerve  just  used  in  its 
entire  length,  and  place  it  upon  a  layer  of  cotton  moistened  with  warmed 
saline  solution  (40°  to  45°  C).  Apply  the  electrodes  to  this  stretch  of 
nerve,  and  determine  the  threshold  value  of  the  make  shock  now  re- 
quired to  evoke  a  contraction  of  the  gastrocnemius  muscle.  Quickly 
place  the  nerve  upon  a  piece  of  ice,  and  again  determine  the  threshold  of 
the  least  effective  make  shock.     Compare  the  results. 

3.  Galvani's  Experiment. — Destroy  the  brain  of  a  frog  and  cut  away 
the  forepart  of  its  body.  Also  remove  the  viscera,  ilium,  and  urostyle, 
but  without  injuring  the  roots  of  the  sciatic  nerves.  The  latter  then 
form  the  only  connection  between  the  lower  end  of  the  spinal  cord  and 
the  legs.  Remove  the  skin  from  the  latter  and  pass  a  copper  hook 
through  the  spinal  segment.  Suspend  this  preparation  from  an  ordi- 
nary iron  tripod.  Tilt  the  latter  so  that  the  legs  come  in  contact  with 
the  iron.  Vigorous  contractions  will  result  whenever  the  legs  touch  the 
iron.     Explain,  giving  Galvani's  as  well  as  Volta's  view. 

4.  Action  Current  of  Muscle.  Rheoscopic  Frog. — Prepare  two 
gastrocnemii  muscles  with  long  segments  of  nerve.  Place  both  upon 
a  plate  at  some  distance  from  one  another,  allowing  the  end  of  nerve  A 
to  rest  upon  the  raised  electrodes,  and  nerve  B  of  the  other  muscle 
lengthwise  upon  muscle  A.  Moisten  this  preparation  with  saline,  but 
do  not  allow  any  of  this  solution  to  flow  upon  the  plate.  Arrange  the 
induction  coil  for  stimulation  with  quickly  repeated  shocks.  Stimulate 
nerve  A  briefly,  noting  that  muscle  B  reacts  simultaneously  with 
muscle  A. 

Annotation. — The  impulses  set  up  in  nerve  .1  by  the  stimulation  prcxluce  a 
contraction  of  muscle  .1.  Since  tlie  different  segments  of  this  muscle  do  not  react 
simultaneously  but  successively,  certain  segments  of  it  must  be  at  rest  and  others 
active.  The  active  ones  are  galvanometrically  negative  to  the  resting  ones,  and 
hence  a  difference  in  electric  potential  is  set  up  in  this  muscle  which  is  sufficient  to 

.■)9 


60  ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 

stimulate.     Consequently,  the  response  of  muscle  B  is  the  result  of  impulses  which 
are  produced  in  nerve  B  by  the  current  of  action  of  muscle  A. 

5.  Action  Current  of  Nerve. — Cut  nerve  A  near  the  muscle  and 
place  it  alongside  nerve  B,  so  that  the  two  overlap  for  a  distance  of 
about  2  cm.  Stimulate  nerve  A  briefly  and  note  that  muscle  B  con- 
tracts. 

Annotation. — Nerve  tissue  shows  a  difference  in  potential  in  accordance  with 
the  progressive  activation  of  its  segments.  This  current  of  action  in  nerve  A  is 
responsible  for  the  excitation  of  nerve  B  and  the  contraction  of  the  muscle.  The 
fact  that  it  is  not  due  to  a  direct  escape  of  the  faradic  current  may  be  proved  by 
placing  a  ligatiu"e  upon  nerve  B.  This  effectively  destroys  the  response  of  the 
muscle. 

6.  Action  Current  of  the  Frog's  Heart. — The  fact  that  the  beating 
heart  generates  an  action  current  may  be  easily  proved  by  exposing  the 
heart  of  a  rabbit  during  deep  narcosis  and  placing  the  nerve  of  a  muscle- 


FiG.  37. — The  Rheoscopic  Frog  Prepatation. 
Muscle  A,  stimulated  through  its  nerve  at  S,  generates  an  action  current  which  causes 

muscle  B  to  contract. 

nerve  preparation  lengthwise  upon  its  surface.  The  muscle  then  re- 
sponds to  every  systole  of  this  organ. 

While  the  uninjured  heart  of  a  frog  does  not  show  this  phenomenon 
very  readily,  it  may  be  obtained  in  the  following  way:  Excise  the  heart 
of  a  pithed  frog  and  permit  it  to  continue  its  activity  upon  a  plate. 
Cut  off  its  apex  and  apply  to  it  the  cut  surface  of  the  sciatic  nerve. 
Place  the  more  distant  segment  of  this  nerve  upon  the  surface  of  the 
basal  portion  of  the  ventricle.  The  muscle  then  twitches  with  each 
beat  of  the  heart. 

7.  Paradoxic  Contraction. — The  sciatic  nerve  of  the  frog  divides  near 
the  knee  into  its  peroneal  and  popliteal  branches.  The  fibers  con- 
stituting these  two  minor  nerves  are  not  formed  by  a  splitting  of  the 
distal  axons,  but  arise  separately  from  the  spinal  cord  and  merely  lie 
alongside  each  other  in  the  nerve  itself.  Isolate  the  outer  or  peroneal 
branch  and  divide  it  near  the  knee.  Stimulate  its  central  end  with  a 
brief  faradic  current.     When  a  certain  strength  of  current  is  employed 


MUSCLE    AND    NERVE 


01 


the  muscles  supplied  by  the  popliteal  l)i;iii(vh  will  be  thrown  into  tetanus. 
This  lesult  is  not  duo  to  tho  liaiisinissioii  of  the  nerve  iiriijulsc  in  a  con- 
tripetal  direction  in  the  peroneal  fibers  anti  in  a  centrifugal  direction  in 
the  popliteal  fibers,  but  to  the  excitation  of  the  latter  by  the  action 
current  developed  in  the  former. 

8.  Nerve  Currents. — Moisten  a  piece  of  l«jaliii  in  normal  saline 
solution  and  draw  it  out  in  two  strips  about  1  cm.  in  width  and  6  cm. 
in  length.  Bend  each  at  right  angles  and  hang  them  over  the  edge  of 
a  plate  of  glass'at  a  distance  of  about  6  mm.  from  one  another.     Place 


M.Scior  carpi  uloari 


M.  delloiiieut 

AVrt'.  muieutoevlantut 
M.  blwp«  bncbil 
M.  brach  Intcraiu 
trudlanu* 


M.  supinator  lODgill 
M.  pronator  teres 
M,  flti.  carpi  radialia 

—  M.  flexor  digitor.  suMlm. 

M.  Dex.  polUcis  loogul 
AVrv.  medianits 

M.  abductor  poHlc.  brCT. 
M.  opponens  pollicis 

M.  flex.  poll,  brev, 

M.  adductor  polllc  bre». 


Fig.  38. — Motor  Points  in  Upper  Extremity.     (Howell.) 


the  nerve  of  a  nerve-muscle  preparation  across  these  strips  of  clay, 
allowing  the  muscle  to  rest  upon  the  glass.  Fill  a  small  beaker  with 
normal  saline  solution  and  dip  the  vertical  ends  of  the  clay  into  it. 
The  muscle  contracts  every  time  this  contact  is  made,  because  it  estab- 
lishes a  complete  circuit  for  the  interchange  of  its  own  demarcation 
current. 

9.  Stimulation  of  Motor  Points. — Connect  the  secondary  coil  of  the 
inductorium  by  means  of  wires  of  medium  caliber  with  two  clinical 
electrodes  (see  Fig.  6,  D  and  E),  one  of  which  is  fiat  and  the  other 
pointed.     The  flat,  indifferent  electrode  is  applied  elsewhere  to  the 


62 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


integiiment,  whereas  the  pointed  one  is  used  for  stimulation.     In  order 
to  lessen  the  resistance,  each  electrode  is  equipped  with  a  layer  of  cotton 


Nerv.  ischiadimis 

M.  biceps  fern.  (cap.  long.) 
M.  biceps  fern.  (cap.  brer.)  -~. 


N.  peroneus 
M.  gastrocnem.  (cap.  extern.) 

M.  soleus 
M.  flexor  hallucis  longus 


j-  M.  gluteu 


s  maximus 


M.  adductor  maguus 
M.  semitendinosus 
M.  semimembranosus 


N.  tibialis 

M.  gastrocnem.  (cap.  int.) 
M.  soleus 

M.  flexor  digitor.  comm.  longus 
N.  tibialis 


Fig.  39. — Nekves  and  Motor  Points  in  Lower  Extremity.     {Church  and  Peterson) 

moistened  with  saline  solution.  Localize  different  motor  points,  using 
Figs.  38  and  39  as  guides,  and  stimulate  them  with  break  shocks  of 
moderate  intensity. 


LESSON  IX 

MUSCLE  AND  NERVE  (Concluded) 

ELECTROTONUS.      CATHODIC    AND    ANODIC    EXCITATION.      LAW    OF 
UNIPOLAR  STIMULATION  OF  HUMAN  MUSCLE  AND  NERVE 

1.  Electrotonus. — When  a  nerve  is  traversed  by  a  constant  or  gal- 
vanic current  it  undergoes  certain  physicochemical  changes  which  be- 
tray themselves  in  a  change  in  its  irritability  at  the  points  of  entrance 
and  exit  of  the  current.  When  the  key  is  closed  the  excitation  produc- 
ing the  nerve  impulse  is  had  at  the  cathode  ( — ).  The  anode  (+)  is 
depressed  at  this  time.  On  opening  the  key  the  excitation  is  had  at  the 
anode,  while  the  cathode  is  depressed.  The  former  condition  is  known 
as  anelectrotonus,  and  the  latter  as  catelectrotonus.  Obviously,  during 
the  passage  of  the  constant  current,  we  obtain  only  the  condition  of 
anelectrotonus,  while  the  catelectrotonus  de- 
velops in  the  wake  of  the  current,  i.  e.,  after  /©~  (^ 
it  has  been  broken.                                                          I  j 

Anodic  Depression. — Fasten  two  holders  \zO\-^ 

to  the  rod  in  the  moist  chamber  and  secure  /^l 

in  each  a  non-polarizable  electrode.     A  con-  |      g  ^ 

venient  form  of  the  latter  is  the  clay-boot,        ^- — -^y 

containing  a  rod  of  zinc.     To  begin  with,        0  f"^" 

these  boots  should  be  immersed  in  normal        '^Jl     ||  [ZZJk^f         ,^^S) 

saline  solution  for  a  period  of  about  twenty-  ^-o^,^ 

four  hours  to  render  the  clay  permeable  to  Fig.   40. — Method      of 

the  electric  current.     They  are  then  fastened     Co^DvnoJoFNKRXE^tporLer^ 

in   the   holders.     A   zinc   rod  having  been 

placed  in  each,  the  remaining  space  is  carefully  filled  by  means  of  a 

dropper  with  a  solution  of  zinc  sulphate  (see  Fig.  7). 

Comrcct  in  series  the  binding-posts  upon  the  rods,  a  key,  and  two 
dry  cells.  Place  a  small  tuft  of  cotton  moistened  with  normal  saline 
solution  upon  each  boot.  Make  a  nerve-muscle  preparation,  and  place 
the  nerve  across  the  tufts  of  cotton,  adjusting  the  distance  between  the 
electrodes  to  suit  the  length  of  the  nerve.  Make  and  break  the  current 
by  closing  and  opening  the  key.  With  this  strength  of  current  a  con- 
traction is  obtained  only  on  the  make  of  the  current.  Which  electrode 
is  connected  with  the  carbon  (-|-)  of  the  battery?  Is  the  current  ascend- 
ing or  descending  in  its  direction? 

Ai-range  the  inductorium  for  stimulation  with  single  induction  shocks. 
Apply  the  hand-electrodes  to  any  part  of  the  nerve  and  accurately  de- 
termine the  strength  of  the  make  shock  which  is  required  to  give  a  just 
perceptible  contraction.  Now  close  the  key  in  the  circuit  of  the  constant 
current,  and  while  this  current  is  allowed  to  flow,  stimulate  the  region 

63 


64 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


of  the  anode  of  the  nerve  with  a  make  shock  possessing,  as  has  just  been 
determined,  a  threshold  value.  The  anelectrotonic  diminution  in  the 
excitability  of  the  nerve  will,  in  all  probability,  now  render  this  stimulus 
ineffective. 

If  not  sufficiently  decisive  the  depression  may  be  increased  by  the 
addition  of  another  dry  cell  or  two.  It  eventually  becomes  so  strong 
that  it  prevents  the  passage  of  the  nerve  impulse  developed  at  the 
cathode.  In  order  to  show  this  blocking  effect  place  the  anode  near 
the  muscle,  i.  e.,  render  the  current  ascending.  On  the  make  of  this 
current  the  excitation  is  developed  at  the  cathode.  The  resulting  nerve 
mipulse  travels  toward  the  muscle,  but  never  reaches  it,  because  it  is 
blocked  by  the  area  of  depression  in  the  region  of  the  anode. 

This  point  may  also  be  proved  by  placing  a  drop  of  a  solution  of 
sodium  chlorid  upon  the  nerve  in  the  region  of  the  anode,  the  anode 


Fig.  41. — Method  Used  to  Show  Electrotonic  Changes  on  Making  'and  Break- 
ing OF  Galvanic  Current. 
K,  Key  for  making  and  breaking  of  current;  P,  pole  changer  for  making  either  end 
of  muscle  (M)  anodic  or  cathodic;  D,  clamp  applied  to  muscle  to  destroy  contraction 
wave,  but  not  wave  of  excitation;  W,  weight  sattached  to  ends  of  muscle.  These  may 
be  displaced  by  writing  levers. 

being  in  this  case  situated  near  the  muscles.  Presently  the  muscles  of 
this  leg  will  begin  to  twitch  and  finally  become  tetanically  contracted. 
Close  the  key  in  the  circuit  of  the  constant  current.  The  excitability  of 
this  region  now  having  been  diminished,  the  muscles  will  relax  or  at 
least  show  a  slighter  degree  of  tetanus.  Quickly  change  the  wires  so 
that  the  cathode  comes  to  lie  near  the  muscle.  The  limb  again  becomes 
tetanic.     Repeat  this  test. 

Knowing  these  facts,  explain  the  third  phase  of  the  law  of  Pfliiger, 
pertaining  to  the  effect  of  the  constant  current  upon  normal  excised 
muscle  and  nerve. 

2.  Cathodic  and  Anodic  Excitation. — When  the  constant  current  is 
made,  the  stimulation  arises  at  the  cathode,  and  when  broken,  at  the 
anode.     Suspend  a  sartorius  muscle  of  a  curarized  frog  vertically  from 


MUSCLE    AND    NEUVE  65 

a  hook.  Place  two  noii-poliuizahlc  elect rodos  against  the  opposite 
borders  of  its  upper  portion.  Make  and  break  the  current.  When 
made,  the  nniscle  deviates  toward  the  cathode,  and  when  broken, 
toward  the  anod<'. 

Slit  this  muscle  longitudinallj^  to  near  its  upper  end.  Place  a  piece 
of  rubber  membrane  between  its  two  halves  and  adjust  a  non-polariz- 
able  electnjde  upon  the  surface  of  each.  On  the  make,  its  cathodic 
half  will  coiitrnct,  and  on  the  break,  its  anodic  half. 

Isolate  the  opposite  sartorius  muscle  with  its  attachments.  Adjust 
a  screw  clamp  upon  its  central  area  and  tighten  it  sufficiently  so  that 
the  wave  of  contraction  is  blocked  without  impairing  the  conduction 
between  its  two  ends.  SuspcMul  this  preparation.  Connect  each  end 
of  the  nuiscle  separately  by  means  of  a  fine  thread  with  a  writing  lever. 
Adjust  a  non-polarizable  electrode  to  each  end.  Make  and  break  the 
constant  current.  Note  that  the  lever  attached  to  the  cathode  moves 
first  on  the  make,  whereas  the  lever  attached  to  the  anode  rises  first 
on  the  break  (Fig.  41). 

3.  Law  of  Unipolar  Stimulation  of  Human  Muscle  and  Nerve.— 
Study  the  ari'angcmcnt  and  .action  of  the  apparatu^^,  consisting  of: 
(a)  50  dry  or  moist  cells  connected  in  series,  (h)  a  pole  changer,  and  (c) 
two  clinical  electrodes,  one  of  which  is  broad  and  the  other  pointed. 
The  latter  is  equipped  with  a  key,  by  means  of  which  the  current  may 
be  made  and  broken.  Moisten  the  felt  lining  of  these  electrodes  with 
saline  solution,  and  apply  the  broad  indifferent  one  to  the  shoulder. 
The  pointed  stimulating  electrode  hold  against  the  skin  over  the  ulnar 
nerve,  near  the  internal  condyle  of  the  humerus.  To  begin  with, 
employ  8  cells,  making  and  breaking  the  current  while  the  anode  is 
over  the  nerve.  Reverse  the  current,  so  that  the  cathode  now  lies 
upon  the  nerve.     Repeat  the  stimulations.     Which  stimulus  is  effective? 

Increase  the  strength  of  the  stinuilation  by  the  addition  of  several 
cells  (possibly  4  to  6).  Repeat  the  stimulations  while  first  the  anode 
and  then  the  cathode  lies  over  the  nerve.  Which  stimuh  are  effective? 
Add  other  cells,  and  repeat  the  stimulations.  Tabulate  the  results  and 
compare  them  with  those  forming  the  basis  of  Pfluger's  law  of  polar 
stimulation.  State  why  the  latter  is  not  applicable  to  normal  human 
muscle  and  nerve  in  situ  f 

Annotation. — Normal  human  muscle  and  nerve  give  the  following  results  with 
the  constant  ciurent: 

Weak.  Medium.  Strong. 

ccc     ccc     ccc 

ACC       ACC 

AOC        AOC 

COC 

This  shows  that  the  cathodic  closing  stimulus  is  the  strongest  of  all,  and  the  cathodic 
opening  stimulus  the  weakest.     E.xplain  these  results. 


LESSON  X 
THE  BLOOD 

THE  COAGULATION  OF  THE  BLOOD.    COUNTING  OF  THE  BLOOD- 
CORPUSCLES 

\.  Preparation  of  the  AnimaL — Place  a  cat  under  the  l)ell-jar,  con- 
taining a  small  sponge  moistened  with  ether,  and  carefully  note  its 
l)ehavior  during  the  consecutive  stages  of  the  narcosis.  When  fully 
under  the  influence  of  the  ether  transfer  the  animal  to  the  operating 
tal)le,  and  apply  a  mask  to  its  mouth,  maintaining  the  anesthesia 
throughout  the  following  experiments. 

Annotation. — Like  in  operations  upon  human  heings,  tlie  (lei)th  of  the  narcosis  is 
ascertained  by  the  intensity  of  the  corneal  reflex.  On  touching  the  eornea  the  eyelids 
are  flose<l.  The  ([uiflcness  with  wliifh  tliis  reaction  takes  place  serves  as  a  guide  in 
administering  the  ether.  If  the  reHex  becomes  sluggish  in  its  cliaracter,  give  less 
ether.  If  the  reflex  is  aholislied  entirely,  institute  artificial  respiration  immediately 
imtil  the  respiratory  movements  are  again  executed  spontaneously.  Also  watch 
the  character  of  the  respiratory  movements,  and  note  the  size  of  the  pupil,  because 
the  al)olition  of  the  refle.xes  is  accompanied  by  an  extreme  dilatation  of  the  pupil. 
Tiie  action  of  the  heart  usually  ceases  some  time  after  the  stoppage  of  respiration, 
and  hence  it  is  possil)le  to  resuscitate  the  animal  if  prompt  measures  are  taken. 
The  abdominal  reflex  may  also  be  employed  as  a  guide.  On  tapjiing  upon  the  abdo- 
men of  the  animal  with  the  flat  of  the  hand  the  alidominal  nuiscles  contract,  render- 
ing tlie  alxlominal  wall  tense.  Obviously,  if  the  narcosis  has  l)een  carried  too  far, 
tills  reaction  does  not  take  i)lace,  and  the  hand  does  not  rebound. 

A  very  efficient  narcosis  may  also  be  established  liy  means  of  urethane  or  chloral. 
Chloretone  is  administered  in  doses  of  0.25  gram  per  kilo  of  weight.  Dogs  should 
receive  ^  to  ^  gr.  of  morphin  and  ^\^  to  y^o  gr-  of  atropin  sulj^hate  a!)Out  thirty  minutes 
before  ether  is  given.  When  chloral  is  administered  the  animal  should  be  kept 
warm,  otherwise  an  excessive  loss  of  heat  may  result.  Ether  narcosis  is  adhered  to 
in  these  experiments  in  order  to  gi^•e  the  student  as  much  experience  as  possible 
preparatory'  to  his  clinical  work. 

Tracheotomy.  Insertion  of  Cannula. — Insert  ai  cannula  in  the  trachea 
and  connect  it  with  a  glass  bottle  containing  a  sponge  moistened  with 
ether.  Expose  the  right  common  carotid  artery  and  left  external 
jugular  vein  and  insert  a  straight  glass  cannula  in  the  central  end  of 
the  former  and  the  distal  end  of  the  latter  blood-vessel. 

Annotation. — The  operation  of  tracheotomy  is  performed  in  the  following  man- 
ner: Make  a  median  incision  in  tiie  skin  of  the  neck,  begiiming  about  2  cm.  below 
the  larjTix.  Lay  the  scalpel  aside  and  cut  tlirough  the  underlying  fascia  with  the 
scissors.  With  the  help  of  two  forceps  separate  the  nnisdes  in  the  median  line 
until  the  trachea  is  brought  into  view.  Separate  the  latter  from  the  fascia  surround- 
ing it,  and  draw  a  loose  cotton  ligature  around  it.  Witii  your  left  hand  raise  the 
trachea  sufficiently  to  be  able  to  make  a  transverse  incision  between  two  adjoining 
rings  of  cartilage.  Cut  forward  through  two  rings  of  cartilage.  Quickly  insert  the 
short  arm  of  the  tracheal  cannula  through  this  opening  and  tie  the  ligature  around 

(i7 


68  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

it.  To  hold  it  firmly  in  place  carry  this  ligature  also  around  the  free  end  of  the 
cannula.  Connect  the  latter  by  means  of  a  piece  of  large  rubber  tubing  with  the 
ether  bottle. 

In  inserting  a  cannula  in  the  carotid  artery  proceed  as  follows:  Identify  the 
sternocleidomastoid  muscle.  Loosen  its  inner  border  from  the  neighboring  tissues 
by  means  of  the  blunt  end  of  forceps.  Retract  the  muscle  laterally  outward.  In 
the  bottom  of  the  woimd  will  be  found  the  carotid  artery,  internal  jugular  vein,  and 
vagus  nerve.  The  carotid  artery  is  easily  recognized  as  a  pulsating  blood-vessel 
of  considerable  size.  While  your  assistant  retracts  the  margins  of  the  wound,  free 
the  artery  from  its  sheath  by  means  of  two  forceps.  Place  a  silk  ligature  around 
it  and  tie  it.  Grasp  the  ligature  between  the  thumb  and  middle  finger  of  your  left 
hand,  and  allow  the  artery  to  rest  upon  the  tip  of  your  index-finger.  Apply  to  it  a 
spring  clip  at  a  distance  of  about  2  cm.  centrally  to  the  ligature.  By  means  of  scis- 
sors held  in  your  right  hand  make  a  transverse  incision  in  the  artery  at  a  distance 
of  about  2  mm.  centrally  to  the  ligature.  Insert  the  beveled  end  of  a  straight  glass 
cannula  through  this  opening  (toward  the  heart),  and  secure  it  by  means  of  a  silk 
ligature. 

In  inserting  a  cannula  in  the  distal  end  of  the  external  jugular  vein  the  same 
procedure  is  to  be  followed.  Make  an  incision  along  the  outer  margin  of  the  sterno- 
cleidomastoid muscle.     Reflect  the  skin  outward  by  separating  it  from  the  fascia 


Fig.   42. — Tracheal   Cannula.  Fig.  43. — ^Artery  Clamp. 

{Harvard  Apparatus  Co.) 

underneath.  Cut  close  to  the  skin,  because  this  vein  lies  very  superficial  and  is 
easily  compressed.  It  is  recognized  by  its  large  caliber  and  dark  color  which  sharply 
contrasts  it  against  its  investment  of  fatty  tissue.  Isolate  it  for  a  distance  of  3  or 
4  cm.,  and  ligate  it  with  a  silk  thread.  Apply  a  spring  clip  about  2  cm.  distally  to 
the  ligature.  Incise  it  transversely  in  the  manner  just  described  and  insert  a  can- 
nula, securing  the  latter  by  means  of  a  silk  ligature.  Since  the  vein  collapses  after 
the  incision  the  opening  is  sometimes  not  easily  found.  The  spring  clip  may  then 
be  opened  momentarily  to  allow  a  few  drops  of  blood  to  escape.  Always  use  a 
cannula  of  about  the  same  caliber  as  that  of  the  blood-vessel  into  which  it  is  inserted. 

2.  Arterial,  Venous,  and  Asphyctic  Blood. — Release  the  spring  clips 
upon  the  artery  and  vein  sufficiently  to  allow  the  cannulas  to  become 
filled  with  blood.  Observe  the  difference  in  color.  Explain.  Close 
the  tracheal  tube  for  a  short  time  until  the  animal  shows  forced  respira- 
tory movements.  Release  the  cHp  upon  the  artery,  and  allow  the  blood 
in  this  cannula  to  be  displaced  by  fresh  blood.  What  is  the  color  of 
the  latter?  Compare  it  with  that  of  the  venous  blood  previously  with- 
drawn.    Explain  this  difference.     Clean  both  cannulas  thoroughly  by 


THE    MLOOI)  69 

means  of  a  small  plug  of  cotton  fustcnocl  t(j  the  roughened  end  of  a  short 
wire. 

Annotation. — In  oporations  upon  animals  tho  work  shoiiKi  ho  dividcfl  in  such  a 
way  that  every  student  lias  iiis  own  particular  task  to  perform.  Thus,  one  .should 
he  assijijned  to  f^ive  etiier,  another  to  perform  the  tracheotomy,  and  still  another  to 
cannulai/,e  the  artery.  During  the  ne.xt  lahoratory  peri(Ml  the  students  should  he 
made  to  rotate,  so  that  each  has  a  ditt'erent  task  to  p<'rform. 

3.  Coagulaiion  of  the  Blood. — Expose  the  opposite  external  jugular 
vein  widely.  Place  two  ligatures  about  3  mm.  apart  around  its  central 
portion.  Ag'fiin  ligate  twice  its  distal  portion.  Remove  the  interven- 
ing segment  of  vein  in  its  entirety  by  cutting  between  the  two  central 
and  two  peripheral  ligatures.  Suspend  this  preparation  for  a  period  of 
about  forty  minutes.     Meanwhile  perform  the  following  experiments. 

Annotation. — Unless  the  walls  of  the  \('in  have  heen  injured  the  hlood  in  this 
segment  will  remain  fluid  for  an  indefinite  period  of  time,  hecause  no  agent  is  present 
therein  to  destroy  the  thrombocytes  and  to  liberate  thrombokinase. 

Withdraw  a  small  quantity  of  blood  from  the  artery  into  a  watch- 
glass  and  observe  the  formation  of  the  coagulum. 

Allow  a  drop  of  blood  to  fall  upon  a  glass  shde,  and  observe  under 
the  microscope  the  clumping  of  the  corpuscles  produced  by  the  deposi- 
tion of  fibrin  shreds. 

Draw  blood  into  a  beaker  and  vigorously  whip  it  for  a  few  minutes 
with  a  roughened  piece  of  wood.  Wash  the  fibrin  attached  to  the  stick, 
and  note  its  appearance,  texture,  and  elastic  properties.  State  why 
blood  from  which  the  fibrin  has  been  removed  remains  fluid.  Thor- 
oughly cleanse  the  cannula. 

Collect  a  few  cubic  centimeters  of  blood  in  a  test-tube  and  upon  a 
plate.     Which  specimen  clots  more  rapidly? 

Annotation. — Since  the  walls  of  the  test-tube  present  a  larger  destructive  sur- 
face to  the  blood,  this  portion  will  clot  more  speedily. 

Draw  a  small  quantity  of  blood  into  a  test-tube  about  1  cm.  in 
diameter.  Note  the  time  of  its  withdrawal.  Hold  the  test-tube  steady 
in  your  hand,  slightly  tilting  it  after  one  minute  and  again  at  intervals 
of  one-half  minute  until  it  can  be  inverted  without  the  blood  flowing 
out.  The  time  intervening  between  the  withdrawal  of  the  blood  and 
its  coagulation  is  known  as  the  coagulation  time. 

Withdraw  a  sample  of  blood  into  a  test-tube  and  place  the  latter  in 
crushed  ice.  Since  cold  retards  all  chemical  processes,  it  prolongs  the 
coagulation  time. 

Withdraw  equal  quantities  of  blood  into  two  test-tubes,  one  of 
which  has  been  thoroughly  anointed  with  vaselin.  Give  an  explana- 
tion for  the  fact  that  the  blood  in  the  latter  clots  less  speedily. 

Draw  blood  into  one-quarter  of  its  volume  of  a  1  per  cent,  solution 
of  potassium  oxalate.     Explain  the  fact  that  this  blood  remains  fluid. 


70  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

Later  on  add  a  few  drops  of  a  2  per  cent,  solution  of  calcium  chlorid. 
Does  this  blood  clot?     Explain. 

Draw  blood  into  one-quarter  of  its  volume  of  a  saturated  solution 
of  magnesium  sulphate.     Give  a  reason  for  its  remaining  fluid. 

Thoroughly  cleanse  the  glass  cannula,  and  connect  it  with  a  short 
curved  tube.  Allow  blood  to  enter  this  tube  until  the  air  has  been 
expelled  from  it.  Then  dip  the  tube  into  a  receptacle  filled  with  mer- 
cury and  allow  a  small  quantity  of  blood  to  collect  over  mercury  con- 
tained in  a  narrow  vessel.  Does  this  blood  which  has  not  come  in  con- 
tact with  air  clot? 

Annotation. — Air  is  not  an  essential  factor  in  the  coagulation  of  the  blood,  and 
hence  a  perfect  clot  is  obtained  under  this  condition. 

"Draw  a  small  quantity  of  blood  into  a  test-tube.  Add  a  few  drops 
of  distilled  water.  Note  the  changes  in  the  color  and  general  appear- 
ance of  this  blood.  Give  their  cause.  Blood  so  hemolyzed  is  known  as 
laked  blood. 

To  a  thin  layer  of  blood  collected  upon  a  slide  add  a  drop  of  a  solu- 
tion of  bile  salts.  Note  under  the  microscope  the  rapid  destruction  of 
the  red  corpuscles. 

To  another  layer  of  blood  add  a  drop  of  a  hypertonic  solution  of 
sodium  chlorid.  Study  under  the  microscope  the  abnormal  types  of 
red  cells.     Make  sketches  of  them  in  different  stages  of  crenation. 

4.  Relative  Amounts  of  Plasma  and  Corpuscles. — Collect  30  c.c. 
of  blood  in  a  test-tube.  Immediately  place  it  in  the  centrifuge  opposite 
a  test-tube  of  the  same  size  filled  with  water.  Centrifugalize  for  a 
period  of  five  minutes.  What  is  the  proportion  of  plasma  and  cor- 
puscles? 

5.  Enumeration  of  the  Red  Corpuscles. — Collect  a  drop  of  blood  in 
a  watch-glass.  Dip  into  it  the  end  of  a  counting  pipet  (Thoma-Zeiss) 
and  aspirate  gently  upon  the  rubber  tube  until  the  pipet  has  been  filled 
with  blood  to  line  1.  Quickly  cleanse  its  end  with  a  piece  of  filter- 
paper  and  dip  it  into  Hayem's  fluid.  Aspirate  until  the  bulb  of  the 
pipet  has  been  filled  to  line  101.  Shake  the  tube  well.  Allow  a  drop 
or  two  of  this  mixture  to  escape  and  place  the  next  one  upon  the  raised 
base  of  the  counting  chamber.  Do  not  allow  it  to  overflow  into  the 
space  next  to  the  base.  Replace  the  cover,  and  determine  under  the 
microscope  the  number  of  red  cells  in  20  squares.  Take  the  average 
and  multiply  this  figure  by  100  and  4000. 

Annotation. — Since  each  square  covers  an  area  of  400  sq.  mm.  and  has  a  capacity 
of  4A0  c.mm.,  1  c.mm.  must  contain  4000  times  the  average  number  found  in  these 
squares.  Moreover,  since  the  dilution  is  1  :  100,  the  number  of  red  corpuscles  in  1 
c.mm.  of  blood  must  correspond  to  the  number  of  red  cells  in  a  square  X  4000  X  100. 

Hayem's  fluid  contains  2  grams  of  sodium  chlorid,  10  grams  of  sodium  sulphate, 
1  gram  of  corrosive  subhmate,  and  400  grams  of  water. 

The  pipet  is  cleaned  by  drawing  distilled  water  through  it,  then  alcohol,  and 
lastly  ether.     A  current  of  air  is  passed  through  it  from  a  rubber  bulb  until  dry. 


THE    BLOOD 


71 


The  counting  chamber  is  cleaned  with  distilled  water  and  nothing  rougher  than  a 
caniel's-hair  brush.     Do  not  use  aleoiiol  or  etiier. 

().  Enumeration  of  the  White  Corpuscles. — Proceed  as  before,  but 
dilute  the  blood  with  a  1  per  cent,  solution  of  acetic  acid.  This  agent 
destroys  the  red  corpuscles.     The  dilution  usually  made  is  1  :  200. 


n 


r? 


-  101 


W 


Fig.  44. — Hemocytometer.     (Thoma-Zeiss.) 

A,  Pipet;  B,  glass  bead;  C,  counting  chamber  seen  from  side;  D,  counting  chamber  seen 

from  above;  E,  field  as  seen  under  microscope. 

7.  Hemorrhage. — Remove  the  clip  from  the  carotid  artery  and  allow 
the  blood  to  escape  into  a  tall  beaker.  Notice  the  differences  in  the 
force  of  the  flow  and  the  changes  in  the  character  of  the  respiratory 
movements,  resulting  in  consequence  of  the  progressive  anemia  and 
insufficient  aeration  of  the  tissues  (hemorrhagic  dyspnea).  Kill  the 
animal  by  giving  an  excessive  amount  of  ether. 

Place  the  beaker  with  the  blood  in  a  cool  place  and  allow  it  to  stand 
for  twenty-four  hours.  Study  the  appearance  of  the  serum  and  coag- 
ulum  at  the  end  of  this  period. 


LESSON  XI 


THE  BLOOD    Continued) 


THE  COUNTING  OF  HUMAN  BLOOD-CORPUSCLES.    SPECmC  GRAVITY 
AND  APPEARANCE  OF  BLOOD 

1.  Microscopic  Examination  of  Blood. — Pith  u  froji  and  open  tlie 
abdomen.  Incise  the  ventricle  and  allow  a  few  drops  of  blood  to  fall 
into  20  c.c.  of  a  .solution  of  0.7  per  cent,  sodium  chlorid.  Place  a  drop 
of  this  mixture  upon  a  glass  slide  and  examine  the  corpuscles  under  the 
microscope.     Note  their  shape,  size,  and  nucleus. 

Place  a  droplet  of  blood  from  your  finger  upon  a  glass  side  and  spread 
it  out  by  drawing  the  edge  of  a  cover-glass  through  it.  Note  the  shape 
and  size  of  the  corpuscles.  Move  the  cover-glass  slightly  so  as  to 
obtain  a  lateral  view  of  some  of  them.     Note  their  shape. 

Insert  a  thin  layer  of  porous  wood  under  tlie  skin  of  the  dorsal 
lymph-sac  of  a  normal  frog.  Allow  it  to  remain  there  for  twenty-four 
hours.  Remove  it  and  carefully  wash  it  in  a  few  drops  of  normal  saline. 
Place  a  drop  of  the  latter  upon  a  slide  and  examine  it  for  leukocytes. 
Study  the  movements  of  one  of  these,  making  sketches  in  gross  outline 
at  intervals  of  three  minutes.  If  not  actively  moving,  gently  warm  the 
slide  over  an  alcohol  lamp.  Add  a  few  granules  of  powdered  India-ink 
and  observe  the  manner  in  which  the  leukocytes  envelop  this  foreign 
substance. 

2.  Counting  of  Human  Red  Cells. — Wash  the  tip  of  your  finger 
with  a  cloth  moistened  in  alcohol.  Allow  it  to  dry.  Pierce  the  skin 
of  its  dorsal  surface  with  a  lancet-shaped  needle  and  squeeze  the  tissues 
to  obtain  a  droplet  of  blood  as  quickly  as  possible.  Count  the  number 
of  the  red  coi-puscles  in  the  manner  described  in  the  preceding  lesson. 
Obtain  a  fresh  droplet  of  blood  and  determine  the  number  of  the  leu- 
kocytes. 

3.  Simultaneous  Count  of  Red  and  White  Corpuscles.— Proceed  as 
described  above  when  counting  the  red  cells  alone.  Add  a  stain  to  the 
diluting  fluid  that  will  color  the  white  cells  only,  for  example: 

Methvl  violet,  0.025  gram 

Sodium  chlorid,  1.0 

Distilled  water,  100        c.c. 

Count  the  red  cells  in  a  group  of  36  spaces.  Then  count  the  white 
cells  in  all  of  the  9  square  millimeter  spaces.  Repeat  with  two  or  three 
different  samples.  Obtain  the  average.  Multiply  by  4000  and  again 
by  100. 

4.  Estimation  of  the  Percentage  of  Hemoglobin. — Procure  a  Fleischl 
hemoglobinometer,  glover's  needle,  and  a  small  beaker.     The  metaUic 

73 


74  ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 

cup  of  the  aforesaid  instrument  is  divided  into  two  compartments  of 
equal  size,  and  has  a  glass  bottom  and  detached  glass  top.  Added  to 
it  is  a  glass  capillaiy  tube  held  in  a  narrow  metallic  handle. 

Cleanse  the  metallic  cup  thoroughl}^  with  water  and  dry  it  with  a 
cloth  if  necessarj'.  Also  cleanse  the  capillary  tube  with  water  and 
hydrogen  peroxid,  and  then  again  with  water.  Dry  it  by  blowing  a 
current  of  air  through  it  from  a  rubber  pouch.  Fill  each  side  of  the 
metalhc  cup  with  distilled  water — about  three-fourths  full. 

Collect  a  drop  of  blood  upon  the  lobule  of  the  ear  of  the  subject. 
Hold  the  end  of  the  capillary  tube  horizontally  against  the  drop.  If 
the  tube  is  clean,  it  will  fill  rapidly  by  capillary  attraction.     Remove 


Fig.  45. — Fleischl's  Hemoglobinometer.     (Hall.) 

excess  by  touching  its  end  carefully  with  filter-paper.  Quickly  put  the 
capillary  tube  in  the  water  on  one  side  of  the  metallic  cup.  Wave  it 
back  and  forth  and  finally  allow  a  few  drops  of  distilled  water  from  a 
dropper  to  flow  through  it.  Fill  each  compartment  with  distilled  water 
to  the  brim,  stirring  the  mixture  of  blood  and  water  until  completely 
mixed.     Close  the  cup  with  the  cover-glass. 

Adjust  the  hemoglobinometer  in  front  of  a  gas-lamp  in  a  dark 
room,  so  that  the  light  is  reflected  from  the  mirror  equally  into  the  two 
compartments.  Now,  move  the  colored  glass  slide  until  the  tint  of  the 
diluted  blood  appears  to  be  the  same  as  that  of  the  coloi-ed  slide.  Make 
the  reading.  Repeat  this  procedure  several  times,  resting  your  eyes 
repeatedly.     Obtain    an    average   reading.     Thus,    if   the    colors    are 


THE    BLOOD 


75 


matched,  say,  at  division  oi  75,  the  l)lood  contains  75  per  cent,  of  the 
normal  (luantity  of  lK'moglol)in. 

Annofdtion. — (Iowit's  luMiU)jil()l)iii()iiirt('r,  wliidi  may  also  he  iiscrl,  fonsists  of 
a  iiieasurinj^  i)ipot,  a  jjradiiati'd  tulK',  and  a  scaled  tiihc  containiiif^  a  standard  colored 
solntion.  This  standard  re|)resents  the  color  of  a  1  per  cent,  solution  of  normal 
blood.  The  fjraduated  tui)e  is  marked  in  KM)  or  more  parts,  each  part  representing 
20  c.c.  Till-  capacity  of  the  capillary  tuhe  is  20  c.c.  Thus,  if  the  Mood  e.xaminwl 
is  normal,  it  will  he  necessary  to  add  water  to  mark  1(K)  to  make  the  colors  corre- 
spond. If  the  l>loo<l  is  not  normal,  the  percentage  can  he  read  ofi"  from  the  graduated 
tulx»  ahove  the  diluted  l)lo(}d. 

The  pipetjs  filled  in  the  usual  way  from  a  dro|)  of  blood  collected  upon  the 
lobule  of  the  ear  of  the  subject.  Wi|)e  away  any  excess  of  blotxl  after  it  has  been 
tilled.  Then  blow  the  bloo<l  drop  by  drop  into  the  water.  Shake  this  tube  gently 
until  a  thorough  mixture  has  been  obtained.  Suck  a  few  flrops  of  distilled  water 
into  the  pipet  and  add  this  amount  to  the  mixture.  Place  this  tube  beside  the  one 
containing  the  standard  solution.     Add  distilled  water  droj)  by  drop  until  the  color 


r\/7 


too 


io 


90 

80 

h-70 

—  feo 

—  50 

—  fO 

—  30 
10 

1— 10 


^™ 


rvA 


iOc.m-m. 


A        B  c 

Fig.  46. — Hemoglobinometer. 
.4,  Tube  filled  with  colored  fluid;    B,  tube  for  mixing  blood;  C,  receptacle  for  distilled 
water  with  dropper;  D,  pipet. 


D 

(Gowers.) 


of  the  blood  mixture  corresponds  precisely  with  that  of  the  standard.  Make  the 
reading  at  this  time,  the  percentage  of  hemoglobin  being  indicated  upon  the  grad- 
uated cylinder. 


5.  The  Specific  Gravity  of  the  Blood. — Procure  a  specific  gravity 
bulb  or  hydrometer,  a  cylindric  graduated  glass  tube  about  15  cm.  in 
height,  a  pipet  or  pointed  glass  rod,  a  stirring  rod,  a  glover's  needle,  and  a 
mixture  of  benzol  and  chloroform.  Secure  a  drop  of  blood  in  the  usual 
way  and  allow  it  to  fall  into  this  mixture.  If  the  drop  of  blood  remains 
in  the  center  of  the  mixture,  its  specific  gravit}"-  equals  that  of  the  mixture. 
If  it  rises,  it  is  lighter  than  the  mixture,  and  if  it  gravitates  downward, 
heavier  than  the  mixture.     In  the  former  case,  add  benzol,  and  in  the 


76 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


latter,  chloroform,  until  the  drop  retains  a  central  position.  The  spe- 
cific gravity  of  the  mixture  is  then  determined  by  means  of  the  hy- 
drometer. 

Annotation. — Since  the  specific  gravity  of  normal  blood  varies  with  the  amount 
of  iron  in  the  corpuscles,  it  must  also  vary  with  the  percentage  of  hemoglobin. 
Thus,  the  former  corresponds  to  the  following  values  of  hemoglobin : 

1.033  to  1.035  =  25  to  30  per  cent.  Hb. 

1.035  to  1.038  =  30  to  35 

1.038  to  1.040  =  35  to  40 

1.040  to  1.045  =  40  to  45 

1.045  to  1.048  =  45  to  55 

1.048  to  1.050  =  55  to  65 

1.050  to  1.053  =  65  to  70 

1.053  to  1.055  =  70  to  75 

1.055  to  1.057  =  75  to  80 

1.057  to  1.060  =  85  to  90 


LESSON  XII 

THE  BLOOD  (Concluded) 

MEDICOLEGAL  TESTS  FOR  BLOOD 

1.  Spectroscopic  Examination  of  Blood. — Place  a  lew  drops  of  blood 
in  tlic  glass  cell  piovidcd  for  this  pui-posc.  Dilute  it  with  water  until 
a  0.8  per  cent,  solution  has  l)een  obtained.  Examine  it  with  a  spectro- 
scope. Identify  the  «  and  i'^  bands.  Burn  a  few  crystals  of  sodium 
in  the  flame  to  produce  a  distinct  Fraunhofer  D  line. 

Make  a  sketch  showinf>;  the  precise  position  and  character  of  these 
absorption  bantls. 


Fig.  47. — Spectroscope. 

P,  Glass  prism;  A,  collimator    tube,    showing   the   slit,  <S,  through    which    the    light  is 

admitted;  B,  telescope  for  observing  the  spectrum.     (Howdl.) 

Reduce  the  oxyhemoglobin  in  the  above  solution  by  the  addition  of 
a  few  drops  of  Stoke's  fluid.  Repeat  the  examination.  Identify  the 
r  band. 

Add  to  diluted  blood  a  solution  of  caustic  soda  or  potash,  and  warm. 
Reduce,  and  examine  spectroscopically. 

Annotation.- — Greater  concentrations  than  O.6.")  per  cent,  produce  a  coalescence 
of  the  a  and  jS  bands,  while  very  (hhite  solutions  (0.01  to  0.().'>  per  cent.)  give  rise  to 
a  single  band,  near  the  I)  line.  Employ  solutions  of  0.1  to  0.0  per  cent,  and  use  a 
cell  the  inner  width  of  which  measures  1  cm. 

Stoke's  reducing  fluid  consists  of  a  solution  of  ferrous  suli^hate,  to  which  a  little 
tartaric  acid  has  l)een  added.  When  used,  add  annnonia  till  its  reaction  becomes 
alkaline.     Its  color  then  changes  from  yellow  to  dark  yellow. 

77 


78 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


2.  Examination  of  Suspected  Blood. — Dissolve  a  small  quantity  of 
the  suspected  blood  in  normal  saline  solution.  Search  for  corpuscles 
and  apply  the  hemin  test.  Dissolve  a  small  portion  of  the  same  ma- 
terial in  water  or  in  a  dilute  solution  of  caustic  soda  or  potash  and  make 
a  spectroscopic  examination  as  described  in  the  preceding  paragraphs. 

Annotation. — The  student  should  at  this  time  be  shown  the  lytic  and  precipitin 
reactions  of  blood-sera.  Since  it  often  takes  several  weeks  to  sensitize  an  animal, 
these  tests  for  blood  cannot  be  performed  by  students  individuall3^ 

3.  Hemin  Crystals. — Place  a  drop  of  blood  upon  a  glass  slide  and 
dry  it  slowly  in  the  gas  flame.  Add  a  few  crystals  of  sodium  chlorid  and 
a  drop  of  glacial  acetic  acid.  Cover  and  gently  heat  until  bubbles  of 
gas  are  given  off.     Hemin  crystals  appear  as  minute,  dark  brown, 


Fig.  48. — Diagram  of  Spectroscope. 


rhombic  crystals  which  cannot  well  be  confounded  with  the  irregular 
colorless  crystals  frequently  seen  in  preparations  of  this  kind. 

4.  Blood  Crystals. — Mix  a  drop  of  rat's  blood  on  a  slide  with  a  drop 
of  water.  After  about  five  to  ten  minutes  crystals  of  oxyhemoglobin 
will  be  seen  to  form. 

5.  Chemical  Tests  for  Blood. — Add  a  small  quantity  of  blood  to 
tincture  of  guaiacum.  Add  a  little  hydrogen  peroxid  to  this  mixture. 
The  blue  color  ensuing  is  due  to  the  iron-containing  radical  in  hemo- 
globin. Repeat  this  test  with  blood  which  has  been  boiled.  The  same 
reaction  results. 

Dilute  a  little  blood  until  practically  colorless.  Add  to  it  a  few 
drops  of  benzidin  dissolved  in  glacial  acetic  acid  and  a  few  drops  of 
hydrogen  peroxid.  A  blue  color  develops.  Repeat  this  test  with  blood 
which  has  been  boiled.     The  reaction  is  now  less  intense. 


LESSON  XIII 
THE  HEART 

REGISTRATION  OF  THE  HEART-BEAT.  REFRACTORY  PERIOD.  EXTRA- 
SYSTOLE.  EXCISED  HEART.  ACTION  OF  STRIPS  OF  VENTRICULAR 
TISSUE 

1.  Normal  Heart-beat. — Apply  a  lifiatiiro  to  the  nock  of  an  pthorizcfl 
turtle  directly  Ix'hiiid  tiie  occiput,  and  destroy  the  hrain  by  pithing. 
Saw  through  the  lateral  aspect  of  the  ventral  shield  or  plastron,  and 
remove  the  latter  by  cutting  through  the  soft  parts  connecting  it  with 
the  internal  structures.  Keep  close  to  the  bone  so  as  to  avoid  the  large 
blood-vessels.  Identify  the  different  superficial  organs  and  note  the 
texture,  extent,  and  mode  of  attachment  of  the  pericardial  sac.  Incise 
the  latter  by  a  longitudinal  cut  and  separate  the  apex  of  the  heart  by 
dividing  the  strong  band  of  connective  tissue  which  unites  it  with  the 
frenum.  This  band  should  be  preserved  to  serve  later  on  as  an  attach- 
ment for  the  hook  of  the  writing  lever. 


Fig.  49. — ARR.\N-ci;.MEN-T  for  Registering  the  Contractions  of  the  Frog's  Heart. 
(Univ.  of  Missouri  Lab.  Outlines.) 

Identify  the  venae  cavae,  sinus  venosus,  the  right  and  left  auricle, 
and  the  ventricle  with  its  conus  and  main  arterial  trunks  (aortae). 
Note  the  color  and  shape  of  the  ventricle  on  systole  and  diastole,  and 
study  the  sequence  of  contraction  of  the  different  segments  of  the 
heart,  viz.,  sinus,  auricles,  ventricle. 

Insert  a  small  hook  in  the  apical  band  and  connect  it  with  a  writing 
lever.  Counterpoise  the  latter  sufficiently  to  place  the  ventricle  under 
a  slight  tension.  Be  sure  that  the  plate  upon  which  the  turtle  is  resting 
is  placed  vertically  under  the  writing  lever,  so  that  the  heart  is  drawn 


80  ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 

upwaiTd.  Allow  the  ventricle  to  register  its  cycles  upon  the  smoked 
paper  of  a  slowly  revolving  kymograph  above  the  record  of  a  chrono- 
graph beating  once  in  every  two  seconds.  What  is  the  rate  of  the 
heart  per  minute?  Register  the  auricular  beats  in  the  same  manner 
after  having  previously  inserted  the  hook  in  the  wall  of  one  of  the 
auricles.  Note  that  the  rhythm  is  the  same  in  the  two  records,  and 
that  the  force  of  the  contractions  of  the  ventricle  is  much  greater  than 
that  of  the  auricles. 

Annotatioti. — ^'el•y  good  records  may  also  be  obtained  from  the  heart  of  a  frog. 
The  animal  is  pithed  in  the  usual  way  and  fastened  to  a  board  by  means  of  wire 
clips.  A  median  incision  is  then  made  through  the  skin  over  the  sternum,  and  the 
episternum  raised  with  a  pair  of  forceps.  The  edges  of  the  sternum  are  cut  through 
and  the  bone  removed  in  its  entirety.  The  pericardium  is  then  lifted  up  and  divided, 
thus  exposing  the  beating  heart.  The  sinus  ^■enosus  of  this  heart  is  formed  by  the 
imion  of  the  large  inferior  vena  cava  and  the  two  smaller  superior  venae  cavse. 
It  is  continuous  with  the  right  auricle  and  ventricle.  The  latter  continues  as  the 
bulbus  aortje,  which  gives  origin  to  the  two  aortse.  From  the  latter  arise  the  pul- 
monary arteries  which  supply  the  lungs.  From  here  the  blood  is  returned  to  the 
left  auricle,  whence  it  is  again  forced  into  the  ventricle. 


Fig.  50. — Record  of  the  Contractions  of  the  Frog's  Heart. 
The  time  is  registered  in  seconds. 

The  registration  may  be  effected  in  two  ways,  namely,  by: 
(o)  The  Supporting^ Method.— A  vertical  rod  of  straw  is  fastened  by  means  of 
a  thin  wire  to  the  long  arm  of  an  ordinary  writing  lever.  The  joint  between  them 
should  be  very  loose.  The  other  end  of  this  rod  is  made  cup  shaped  by  means  of  a 
piece  of  wax  molded  to  fit  the  surface  of  the  ventricle.  When  the  latter  contracts 
the  lever  is  raised.  Consequently,  the  systolic  period  is  indicated  by  the  up-stroke 
and  the  diastolic  period  bv  the  down-stroke  of  each  wave. 

(h)  The  Su.fpcJhsion  Method— A  fine  thread  is  attached  to  the  end  of  the  short 
arm  of  an  ordinarv  writing  lever.  It  is  connected  by  means  of  a  small  hook  with 
the  apex  of  the  heart.  The  long  arm  of  the  writing  lever  is  weighted  sufficiently 
to  place  a  slight  degree  of  tension  upon  the  heart.  In  this  case  the  up-strokes  of  the 
record  correspond  to  the  systoles  of  the  organ.  If  a  spring  le^■er  is  employed,  the 
tendencv  of  which  is  to  move  upward,  the  string  must  be  fastened  to  its  long  arm.. 
The  contraction  of  the  heart  then  pulls  the  lever  dov.nward,  whereas  the  steel  sprmg 
attached  to  the  lever  pulls  it  upward  as  soon  as  the  cardiac  musculature  becomes 
passive  during  diastole. 

2.  Effect  of  Temperature.— Allow  the  ventricle  to  register  its  cycles 
upon  the  paper  of  a  slowly  revolving  kymograph.  By  means  of  a  pipet 
allow  a  few  di-ops  of  iced  saline  solution  (5°  to  10°  C.)  to  drop  upon  the 


TMK    UK ART 


81 


heart.  Note  the  rechictioii  in  tlie  rate  and  slowinp;  of  eacli  indivkhial 
beat.  After  the  heart  has  a^aiii  resumed  its  normal  rate  and  ampH- 
tude  of  contraetion  hathe  it  in  the  same  maimer  with  warmed  sahne 
sohition  (20°  to  25°  ('.).  Note  the  increase  in  its  rate,  thie  to  a  greater 
rapi(Uty  of  the  inchvichial  contractions. 

3.  Refractory  Period.  Extrasy stole. — Leave  tlie  heart  in  position, 
])ut  place  its  ventricular  portion  in  the  cup  of  a  heart-holder.  Adjust 
the  writing  lever  upon  its  surface,  and  connect  the  binding-posts  with 


Fig.  51. — The  Heart-holder.     (Porter.) 

the  secondary  coil  of  an  inductorium.  Arrange  the  electric  apparatus 
for  stimulation  with  single  shocks,  and  insert  a  signal  in  the  primary 
circuit.  Place  the  writing  point  of  the  latter  in  the  same  ordinate  with 
that  of  the  heart  lever.  Allow  the  ventricle  to  register  its  cycles  upon 
a  drum  revolving  at  a  moderate  speed.  Stimulate  at  intervals  first 
during  the  systolic  and  then  during  the  diastolic  period  of  the  heart. 
Note  that  the  former  stimuli  remain  without  effect,  whereas  the  latter 
produce  an  extra  contraction  (extrasystole).  While  the  musculature 
is  in  contraction  it  remains  impervious  to  stimuli  (refractory  period). 


CP 


Fig.  52. — Stimulation  of  Frog's  Heart  During  Diastole. 
S,  Moment  of  stimulation;   E,  extra  contraction:   CP,   compensatory   pause. 

4.  The  Transmission  of  the  Wave  of  Excitation. — The  wave  of  exci- 
tation, ordinarily  started  at  the  venous  entrance  of  the  heart,  is  trans- 
mitted in  the  turtle  and  frog  over  muscular  connections  and  activates  its 
different  segments  consecutivel}'.  The  transmission  of  this  impulse  may 
be  interfered  with  by  compressing  these  muscular  bridges  by  means  of 
a  screw-clamp  applied  to  the  auriculo ventricular  junction.  By  grad- 
ually tightening  this  screw  a  degree  of  compression  may  be  established 
which  will  allow  only  some  of  these  waves  of  excitation  to  reach  the 


82  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

ventricle.  Not  all  of  the  auricular  contractions  will  then  be  followed 
bj''  ventricular  contractions.  This  constitutes  the  condition  of  partial 
heart-block. 

5.  The  Excised  Heart. — Raise  the  heart  as  a  whole  by  the  frenum, 
and  divide  the  aortse  and  venae  cavse.  Place  the  excised  organ  in  a 
watch-glass  in  some  of  its  blood  and  cover  it  with  another  watch-glass. 
Count  the  number  of  its  beats,  and  note  that  it  becomes  soft  and 
flaccid  during  diastole  and  adjusts  itself  at  this  time  to  the  surface 
upon  which  it  rests.  Apply  a  drop  of  warmed  saline  solution  to  the 
sinus.  Note  the  increase  in  the  rate  of  this  segment,  which,  in  turn, 
brings  about  a  similar  change  in  the  other  portions  of  the  heart. 

6.  Isolated  Segments  of  the  Heart. — The  fact  that  a  heart  when 
separated  from  the  central  nervous  system  continues  to  beat,  shows  that 
it  is  automatically  active.  Cut  transversely  across  between  the  sinus 
venosus  and  the  auricles.  The  sinus  continues  to  beat,  whereas  the 
rest  of  the  heart  ceases  to  beat  for  a  time.  This  proves  that  the  auricles 
and  ventricle  are  ordinarily  activated  by  a  wave  of  excitation  derived 
from  the  sinus.  After  a  time  the  severed  portion  of  the  heart  develops 
a  beat  of  its  own  and  continues  to  contract  rhythmically. 

Sever  the  ventricle  from  the  auricles.  It  ceases  to  beat,  but  may  be 
made  to  contract  at  any  time  by  stimulating  it,  for  example,  by  pricking 
it  with  the  point  of  a  scalpel.     It  usually  executes  several  beats. 

Cut  off  the  apex  of  the  ventricle,  but  preserve  its  basal  portion. 
The  former  remains  quiescent,  but  reacts  promptly  to  all  stimuli. 
Since  the  apex  is  free  from  nervous  elements,  this  experiment  is  usually 
cited  to  prove  that  the  heart-beat  is  of  myogenic  origin. 

7.  All-or-none  Law. — Suspend  this  preparation  of  the  apical  portion 
of  the  ventricle  by  means  of  two  silk  threads  between  the  writing  lever 
and  the  plate.  Apply  the  hand-electrodes  to  it  and  stimulate  it  suc- 
cessively with  single  induction  shocks  of  different  strength.  Do  you 
observe  a  difference  in  the  amplitude  of  its  contractions?  How  does 
striated  and  non-striated  muscle  tissue  behave  under  these  circum- 
stances?    Inquire  into  the  reason  for  this  difference. 

8.  Isolated  Strips  of  Ventricle. — Fasten  one  pole  of  the  quiescent 
basal  portion  of  the  ventricle  to  the  hook  of  a  weight  resting  upon  the 
bottom  of  a  beaker,  and  its  upper  pole  to  the  hook  and  string  of  a  writ- 
ing lever.  Counterpoise,  so  that  this  preparation  is  under  the  least 
possible  tension.  Pour  a  solution  of  0.7  per  cent,  sodium  chlorid  into 
the  beaker  until  it  fully  covers  this  preparation.  Wait  until  the  latter 
shows  continued  activity  (twenty  to  thirty  minutes),  and  record  suc- 
cessive series  of  contractions  at  intervals  of  ten  minutes.  When  the 
contractions  have  weakened,  add  a  few  drops  of  a  1  per  cent,  solution  of 
calcium  chlorid  to  the  saline.  The  calcium  stimulates  cardiac  muscle 
(systole),  and  hence  the  individual  contractions  should  again  assume 
their  former  amplitude. 

In  small  doses  potassium  favors  the  relaxation  of  cardiac  muscle, 
while  in  larger  doses  it  brings  about  a  continued  diastole.     To  show  this 


THE    HEAHT  83 

effect,  it  may  suffice  to  add  several  drops  of  a  0.9  per  cent,  solution  of 
potassium  chlorid  to  the  saline  solution.  As  soon  as  the  preparation 
has  })ecome  quiescent,  immerse  it  in  fresh  saline  .solution  or  in  Ringer's 
fluid,  which  contains  the  aforesaid  .salts  in  the  following  proportion: 
NaCl,  0.7  per  cent.;  KCl,  0.035  per  cent.;  CaCl-,  0.026  per  cent.  The 
rhythm  will  presently  be  restored. 

Annotation. — Witli  some  rare  a  turtle's  heart  may  Ix-  made  to  last  throughout 
these  experiments.  It"  it  does  not,  use  a  frog's  heart  to  (•om|)lete  this  series.  The 
action  of  tlie  salts  may  also  be  studied  separately  upon  different  hearts.  The  pre- 
ceding order,  however,  should  be  adhered  to,  owing  to  the  possibility  of  saving 
material. 

Conduction  Through  the  Ventricle. — Pith  a  frog  and  expose  the 
heart.  Destroy  the  continuity  of  the  nerve-fibers  in  the  ventricle  by 
makin<z;  four  interdij>itating  cuts  across  it — two  cuts  startinj^  from  its 
left  border  and  two  from  its  right.  Since  the  wave  of  contraction 
nevertheless  descends  over  this  zigzag  strip,  the  wave  of  excitation 
must  be  propagated  by  the  muscular  elements. 

Separate  the  ventricle  from  the  auricles  by  a  transverse  cut.  Note 
that  the  latter  continue  to  beat  synchronou.sly  with  the  sinus,  while  the 
former  remains  quiescent.  Apply  the  hand-electrodes  successively  to 
the  base  and  apex  of  this  zigzag  strip  of  ventricle.  Observe  that  the 
wave  of  contraction  can  thus  be  made  to  travel  from  base  to  apex  as 
well  as  in  the  reverse  direction. 


LESSON  XIV 
THE  HEART  (Continued  > 

INHIBITION  AND  ACCELERATION  OF  THE  SIMPLE  HEART.    ACTION  OF 
NICOTIN.  ATROPIN,  AND  MUSCARIN 

1.  Inhibition  of  the  Heart. — Apply  a  ligature  tijilitly  to  the  neck  of 
an  etherized  turtle  and  destro}'  the  brain  by  pithing.  Remove  the 
ventral  shield  or  plastron  and  clip  away  the  projecting  angles  of  the 
shoulder-blades.  Arrange  the  inductorium  for  stimulation  with  a 
tetanic  current  of  medium  strength.  Hold  the  extended  neck  of  the 
turtle  in  place  and  carefully  isolate  the  vagus  nerve  on  each  side.  Place 
each  in  a  loose  ligature.  Open  the  pericardial  sac  and  connect  the 
apical  band  of  connective  tissue  with  the  writing  lever.     Adjust  the 


Fig.  53. — CotRSE  of  Vagus  Xerve  in  Frog.     (Stirling.) 
SM,   Suhmentalis;  Li',  lung;   I', vagus;   GP,  glossopharyngeal;  HS,  hypoglossal;  L, 
larj-ngeal;  PH,  SH,  GH,  OH,  petro-,  sterno-,  goiiio-,  aud   omohyoid;   HG,  hypoglossus; 
H,  heart;  BR,  brachial  plexus. 

writing  point  of  a  chronograph  underneath  the  writing  point  of  the 
lever.  Raise  the  left  vagus  nerve  and  place  it  upon  the  electrodes. 
Having  recorded  a  number  of  normal  heart-beats,  stinuilate  the  afore- 
said nerve.  If  the  heart  is  not  inhil)ited,  increase  the  strength  of  the 
current,  but  not  excessively,  becau.'^e  an  electrolysis  might  then  result 
which  would  destroy  conduction  permanently. 

Make  a  number  of  these  records,  stimulating  each  time  for  a  few 
seconds.     During  what  period  of  the  cardiac  cycle  is  the  heart  arrested? 

8n 


86 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


Study  the  character  of  the  heart-beats  occurring  directly  after  the 
inhibition.  They  may  be  small  at  first  and  gradually  become  larger, 
or  large  at  first,  and  slowly  decrease  to  normal.  No  explanation  can 
be  given  for  this  difference. 


r 
\ 

r 

lY\l\l 
11  \i  11  \i 

innn, 

mm 

y  11  \l  11 11 

Fig.  54. — Record  of  the  Contractions  of  the  Frog's  Heart  During  Stimulation 

OF  THE  Vagus  Nerve  (Tension  Lever). 

The  time  is  given  in  seconds,  the  stimulation  is  indicated  by  the  signaL 

Stimulate  the  right  vagus  nerve  with  the  same  strength  of  current. 
Do  the  nerves  possess  the  same  inhibitory  power?  They  differ,  but  not 
always  in  the  same  manner,  i.  e.,  the  left  or  the  right  nerve  may  be  more 
powerful,  but  most  generally  the  right.     The  same  differences  may  be 


LAS 


Fig.  55. — Schema  of  the  Sympathetic  Nerve  in  the  Frog. 
OC,  Occiput;  LAS,  levator  anguli  scapulae;  Sym,  sympathetic;  GP,  glossopharyngeus ; 
V-S,  vagosympathetic;  G,   ganglion   of  the  vagus;  Ao,   aorta;  SA,   subclavian  artery. 
(Stirling.) 

noted  in  the  mammals.     Occasionally  a  turtle  will  be  found  in  which 
neither  vagus  possesses  this  function. 

Stimulate  either  vagus  nerve  for  three  or  four  minutes.  Note  that 
the  heart  "escapes"  from  the  inhibition  in  a  very  short  time,  and  sub- 
sequently continues  to  beat  in  spite  of  the  stimulation. 


THK  iiKAirr  87 

Tighten  the  li{i;atiiie.s  upon  both  vugi  nerves.  Apply  a  secuiid  Ujiu- 
ture  to  each  at  a  distance  of  2  mm.  from  the  first.  Cut  between  them. 
Stiniuiate  both  centra!  ends  successively.  Do  you  observe  a  chane;e  in 
the  character  of  the  recoril  now  made?  Stimulate  both  distal  ends 
successively.  Do  you  observe  a  difTerence  between  this  record  and 
that  obtained  previously  with  the  intact  nerve? 

Apply  the  electrodes  transversely  to  the  sino-auricular  region  of 
the  heart.  Stimulate  after  you  have  recorded  a  limited  number  of 
normal  beats.  Does  the  inhibition  produced  in  this  way  differ  from  that 
previously  obtained  by  stinnilatin^  the  vagi  nerves? 

Atniotdtion. — A  very  convenieiit  way  is  to  trcpliiiic  the  ventral  shield  of  the 
turtle  in  tiie  rejtion  of  the  heart.  This  saves  nuich  lal)or  and  jjievents  loss  of  Ijlood 
ami  drying  of  the  tissues.  Moreover,  if  small  pulley-wlieels  are  at  the  dis])osal  of 
the  students,  the  heart  should  he  allowed  to  act  in  its  normal  horizontal  jjosition, 
while  the  string  is  made  to  move  across  the  pulley,  placed  ol)lic|uely  helow  the 
writing  lever.  Do  not  allow  the  heart  to  act  under  too  great  a  tension  and  allow 
it  to  rest  from  time  to  time  hy  disconnecting  the  string.  In  cast'  it  should  cease 
contracting  properly,  ap])ly  a  few  dro])s  of  warmed  saline  solution  to  its  surface. 
Arhythmias  are  not  unconunon  and  may  he  remedied  in  just  this  way. 

2.  Action  of  Nicotin. — By  means  of  a  dropper  apply  a  small  quantity 
of  a  0.2  per  cent,  solution  of  nicotin  to  the  heart.  After  five  minutes 
connect  its  apex  with  the  writing  lever  and  stimulate  the  vagus  nerve. 
The  heart  is  not  inhibited.  Sthnulate  the  sino-auricular  region  directly. 
The  heart  is  inhibited.  What  is  your  conclusion  regarding  the  action  of 
nicotin? 

Annotation. — Nicotin  is  a  nerve-cell  poison  affecting  the  neuron  at  the  synapse. 
In  this  case  it  causes  a  hreak  between  the  vagal  terminals  and  the  recipient  cells 
of  the  inhibitor  plexus  (Remack's),  situated  in  the  region  of  the  sino-auricular  groove. 
Consequently,  the  iniiihitor  impulses  set  up  by  stimulating  the  vagus  can  never  reach 
the  postganglionic  path  and  effector.  The  .stimulation  of  the  plexus  itself  remains 
eti"e<tive,  because  the  |)ostgang!ionic  elements  are  thereby  excited  directly. 

3.  Action  of  Atropin.— Apply  to  the  heart  of  the  same  turtle  a  few- 
drops  of  a  0.5  per  cent,  solution  of  atropin  sulphate.  After  a  few  minutes 
stimulate  the  plexus  situated  at  the  sino-am-icular  junction.  Observe 
that  this  stimulation  now  fails  to  inhibit  the  heart.     Explain. 

Annotation. — This  experiment  should,  of  course,  be  performed  upon  a  fresh 
turtle.  It  will  then  be  found  that  the  atropin  destroys  the  inhibitor  power  of  the 
vagus  as  well  as  that  of  the  plexus  at  the  sino-auricvilar  groove.  This  result  is  due  to 
its  paralytic  effect  upon  the  distal  terminals  of  the  postganglionic  fibers.  Atropin  is 
primarily  a  nerve-fiber  poison.  Since  in  the  above  experiment  the  stimulation  of 
the  vagus  has  already  been  rendered  ineffective  by  the  nicotin,  this  effect  cannot  l)e 
noted.  It  is  for  this  reason  that  a  fresh  turtle  should  be  used  for  the  atropin.  With 
a  class  of,  say,  100  students  this  would  entail  a  consideralile  expense  which  may  be 
avoidefi  by  supplying  this  information  or  by  permitting  one  group  of  stiidents  to  per- 
form the  experiment  with  nicotin,  and  another  the  experiment  with  atropin. 

4.  Action  of  Muscarin. — Apply  to  the  ventricle  of  the  same  turtle 
a  few  drops  of  normal  saline  to  which  a  little  muscarin  has  been  added. 


88  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

A  1.0  per  cent,  solution  of  pilocarpin  acts  in  the  same  way  as  muscarin. 
Note  the  gradual  inhibition  of  the  ventricle. 

Annotation. — It  will  be  remembered  that  this  poison  produces  its  characteristic 
effect  either  by  paralyzing  the  contractile  elements  of  the  muscle-fibers  or  by  stim- 
ulating the  inhibitor  nerve  mechanism.  The  latter  view  seems  the  more  plausible, 
because  if  a  few  drops  of  a  0.5  per  cent,  solution  of  atropin  are  applied  to  a  heart 
which  has  been  arrested  with  muscarin,  this  organ  resumes  its  beat.  Atropin  acts 
antagonistically  to  the  muscarin  by  counteracting  the  effect  of  the  latter. 

5.  Reflex  Cardiac  Inhibition. — Etherize  a  frog  and  lay  it  upon  its 
back.  iMake  a  rounded  orifice  in  the  ventral  surface  of  the  thorax  in  the 
region  of  the  heart  so  as  to  expose  this  organ  fully  to  the  view.  With 
the  flat  handle  of  a  scalpel  continue  to  tap  lightly  upon  the  ventral 
aspect  of  the  abdomen  until  the  heart  shows  a  material  reduction  in  its 
frequenc3\  Explain  this  result,  comparing  it  with  the  symptoms  follow- 
ing strokes  upon  the  solar  plexus  in  man. 

Divide  both  vagi  nerves  and  repeat  this  experiment.  Note  that  the 
aforesaid  procedure  now  fails  to  inhibit  the  heart,  because  the  paths  by 
means  of  which  these  impulses  reach  the  heart  have  been  cut. 

Annotation. — In  the  frog  the  vagi  nerves  are  not  easily  found.  Insert  a  glass 
rod  in  the  esophagus  to  distend  it.  Remove  the  tissues  over  the  petrohyoid  muscle, 
extending  from  the  angle  of  the  jaw  to  the  thyroid  process  of  the  hyoid  bone.  Two 
nerves  will  be  seen  pursuing  a  course  across  this  muscle,  namely,  the  hypoglossal 
and  the  glossopharyngeal.  The  first  is  easily  recognized  by  tracing  its  course  to 
the  tongue.  It  lies  closer  to  the  midline.  Next  to  the  lower  border  of  the  petrohyoid 
muscle  and  close  to  a  blood-vessel  lies  the  vagus  (Fig.  53). 

6.  Acceleration  of  the  Heart. — Arrange  the  apparatus  for  registering 
the  contractions  of  the  frog's  heart  upon  the  smoked  paper  of  a  moder- 
ately rapid  kymograph.  Pith  a  frog  and  expose  the  heart  by  making  a 
median  incision  through  the  wall  of  the  thorax.  Expose  the  spinal 
column  at  the  base  of  the  skull  by  pushing  the  esophagus  and  trachea 
to  one  side.  Identify  the  vagus  ganglion.  It  lies  under  the  upper  part 
of  the  levator  scapulae  muscle.  After  its  formation  the  sympathetic 
nerve  turns  outward  along  the  base  of  the  jaw  to  become  united  with 
the  vagal  fibers.  Black  pigment  marks  the  course  of  this  nerve.  Isolate 
this  portion  and  insulate  it  with  a  narrow  strip  of  rubber  membrane. 
Allow  the  heart  to  register  its  beats  while  the  drum  revolves  once  around 
its  axis  in  about  one  minute.  Add  the  record  of  a  chronograph.  Di- 
rectly underneath  register  a  second  line  of  heart-beats,  but  stimulate 
the  sympathetic  nerve  during  this  entire  period  with  a  tetanic  current 
of  very  moderate  intensity.  Count  the  beats  in  each  line,  and  com- 
pare. The  stimulation  of  this  nerve  in  the  frog  does  not  produce  a  very 
decisive  acceleration;  still,  records  of  this  length  should  show  a  difference 
of  from  ten  to  fifteen  beats. 


LESSON  XV 

THE  HEART  (Continued  i 

STANNIUS*  EXPERIMENT.  STAIRCASE  PHENOMENON.  SUMMATION 
OF  STIMULI.  ACTION  OF  THE  CONSTANT  CURRENT,  ETHER,  AND 
CHLOROFORM.     DISSECTION  OF  THE  MAMMALIAN  HEART 

1.  Stannius'  Experiment.— Pitli  a  fiop;  and  oxposci  the  heail  by  a 
niodian  incision  tinuii}2,ii  the  wall  of  the  thorax.  Use  two  thin  silk 
threads.  Place  one  around  the  sino-auricular  groove,  and  tighten  it 
modoiatoly  until  the  auricles  and  ventricle  cease  beating.  Apply  a 
second  ligature  to  the  auriculoventricular  groove,  and  tighten  it  suf- 
ficiently until  all  three  parts  of  the  heart  beat  again.  Explain  this 
phenomenon. 

2.  Staircase  Phenomenon. — Remove  the  ligature  previously  applied 
to  the  auriculoventricular  groove,  so  as  to  render  the  auricles  and  ven- 
tricle again  quiescent.  Coiuiect  the  latter  with  a  light  heai't  lever 
(suspension  method),  and  stimulate  its  substance  with  single  induction 
shocks  at  intervals  of  five  seconds.  Each  time  move  the  stationary 
drum  a  short  distance.  The  heart  usually  reacts  to  stinuili  of  different 
strengths  by  giving  maximal  contractions,  but  its  amplitude  of  reaction 
is  determined  chiefly  by  its  condition.  In  the  Stannius  preparation 
certain  conditions  have  arisen  which  convert  the  first  four  or  five  con- 
tractions into  an  ascending  series. 

8.  Summation  of  Stimuli. — The  Stannius  preparation  may  also  be 
made  to  show  the  phenomenon  of  summation  of  stimuli.  To  accom- 
plish this  end  separate  the  secondary  coil  from  the  primary  until  the 
break  shock  just  ceases  to  be  effective.  Stimulate  the  heart  with  this 
subminimal  stimulus  in  quick  succession  until  a  contraction  is  obtained. 

4.  Incomplete  Tetanus. — The  Stannius  preparation  may  also  be 
made  to  yield  an  incomplete  tetanus  by  passing  a  quickly  interrupted 
current  through  it. 

.5.  Effects  of  the  Constant  Current. — Remove  the  ligature  which 
has  previously  been  applied  to  the  sino-auricular  groove.  The  heart 
should  resume  its  normal  beat.  If  not,  use  a  fresh  preparation.  Insert 
in  the  frog's  mouth  the  wire  connected  with  the  zinc  of  a  dry  cell 
(cathode).  Place  the  flat  end  of  the  wire  attached  to  the  carbon 
(anode)  upon  the  surface  of  the  ventricle.  As  the  well-filled  ventricle 
contracts,  that  portion  of  it  which  rests  against  the  anode  will  remain 
relaxed  and  present  a  flushed  appearance.  In  this  way  a  local  diastole 
is  produced  in  a  general  field  of  systole.  Suddenly  remove  the  wire, 
breaking  the  circuit.  The  area  just  alluded  to  now  remains  contracted, 
and  shows,  therefore,  a  pale  appearance.  A  local  systole  arises  within 
a  field  of  general  diastole.  This  experiment  may  be  employed  to  show 
that  the  anode  depresses  on  the  make,  but  stinmlates  on  the  break. 

89 


90  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

The  wires  should  now  be  reversed  to  show  the  cathodal  excitation 
on  the  making  and  the  cathodal  depression  on  the  breaking  of  the  con- 
stant current. 

6.  Action  of  Chloroform  and  Ether. — Excise  two  frogs'  hearts  and 
place  each  in  a  watch-glass.  Cover  them  equally  with  a  sufficient 
quantity  of  sahne  solution  (5  c.c).  Add  a  drop  of  pure  chloroform  to 
one  and  a  drop  of  ether  to  the  other.  Note  that  the  heart  in  the  former 
solution  loses  its  tonus  rapidly  and  soon  ceases  to  beat,  while  the  action 
of  the  other  does  not  seem  to  have  been  materially  impaired.  In  order 
to  produce  the  same  effect  with  the  ether,  as  many  as  10  drops  might 
have  to  be  added  to  the  original  solution. 

7.  Dissection  of  the  Mammalian  Heart.- — Procure  the  heart  of  an  ox 
or  sheep.  Ask  to  have  the  "tubes  cut  long,"  Identify  its  different  parts 
and  test  the  relative  thickness  of  the  walls  of  its  chambers.  What  is 
the  functional  significance  of  this  difference  in  the  volume  of  the  mus- 
cle substance?  Identify  the  aorta,  pulmonary  artery,  vense  cavse,  and 
pulmonary  veins.  Note  the  appearance  and  strength  of  the  walls  of 
these  blood-vessels.  Trace  the  coronary  arteries  from  the  arch  of  the 
aorta  and  identify  the  coronary  sinus. 

Explore  the  auricles  and  ventricles  by  inserting  the  index-finger 
through  the  stumps  of  the  different  vessels.  Palpate  the  interauricular 
septum  and  locate  the  fossa  ovalis.  Slit  open  the  two  auricles  and  ex- 
amine their  walls  and  recesses.  Note  that  the  venous  orifices  are  not 
guarded  by  valves. 

Beginning  at  the  apex  of  the  heart  make  a  series  of  transverse  sec- 
tions until  both  ventricles  have  been  opened.  Note  that  the  left  cavity 
is  incised  first  and  possesses  a  much  thicker  wall  than  the  right.  Obtain 
an  unobstructed  view  of  the  tricuspid  and  mitral  valves  by  making  a 
longitudinal  incision  through  the  wall  of  each  ventricle.  Study  the 
appearance  and  distribution  of  the  papillary  muscles,  columnse  carneae, 
moderator  bands,  and  chordae  tendinese.  Approximate  the  valve  flaps 
and  note  the  manner  of  insertion  of  the  chordae  tendinese.  Trace  the 
course  of  the  bundle  of  His. 

Tie  a  short  glass  funnel  in  the  stump  of  the  ascending  aorta.  Hold 
the  heart  vertically  and  pour  water  into  the  funnel.  Observe  that  the 
semilunar  valve  closes,  thereby  preventing  the  water  from  escaping-  into 
the  left  ventricle.  By  means  of  a  long  probe  push  one  of  the  flaps  aside. 
Note  the  rush  of  water  into  the  ventricle.  This  condition  represents 
aortic  insufficiency  (regurgitation).  Repeat  the  experiment  on  the 
right  side.  The  sinuses  of  Valsalva  are  here  more  prominent,  because 
the  vessel  wall  is  much  thinner. 


LESSON  XVI 

THE  HEART  (Continued) 

THE  BEATING  MAMMALIAN  HEART.    HEART-BLOCK.    FIBRILLATION 

1.  The  Beating  Mammalian  Heart  in  Situ. — Test  the  artificial 
I'ospinition  apparatus  to  sec  whether  everything  is  in  proper  working 
conchtion.  Have  the  ether  bottle  and  connecting  parts  leady  for  use. 
Etherize  a  cat  and  maintain  deep  anesthesia  throughout  these  experi- 
ments and  luitil  tlie  animal  has  been  killed. 

Perform  tracheotomy  in  accordance  with  the  directions  given  on 
page  67.  Make  a  median  incision  through  the  skin  covering  the 
sternum.  Cut  through  the  ensiform  cartilage  and  median  line  of  the 
sternum,  taking  sp(>('ial  care  not  to  divide  the  mannnary  arteries. 
Institute  artificial  lespiration,  adjusting  the  volume  of  air  so  as  to  give 
a  normal  degree  of  expansion  to  the  lungs.     Stop  bleeding  by  torsion 


Fig.  56. — Marey's  Tamboi  r. 
a,  Axis  of  lever;  h,  metal  tray  covered  with  rubber  incnilirane,  and  coninmnicating  by 

tube /with  the  cannula. 

and  ligation  of  the  vessels.  Separate  the  walls  of  the  thorax  by  means 
of  a  string  drawn  around  the  board.  Identify  the  pericardium  and 
large  blood-vessels  leaving  and  entering  the  heart. 

Insert  the  end  of  a  small  cannula  thi'ough  an  opening  in  the  peri- 
cardial .sac,  and  secure  it  by  means  of  a  hgatuie.  Connect  its  free  end 
by  means  of  narrow  rubber  tubing  with  a  recording  tambour  adjusted 
against  the  paper  of  a  kymograph.  The  pericardial  sac  acts  in  this 
case  as  a  plethysmograph  and  yields  a  tracing  of  the  volumetric  dif- 
ference's which  the  heart  displays  during  its  cycle.  Detach  the  rubber 
tube  from  the  rcH'ording  drum  and  blow  a  small  quantity  of  air  into  the 
pericardial  sac.  What  influence  does  the  increase  in  intrapericardial 
pressure  exert  upon  the  activity  of  the  heart?  Note  that  this  pro- 
cedure produces  dynamic  conditions  such  as  are  found  in  pericarditis. 

(3pcn  the  pericardial  sac  widely  and  i-eflect  the  pericardium  upwai'd. 
Note  the  character  of  the  fiuid  escaping  through  the  incision.  What  is 
its  function?     Identify  the  different  parts  of  the  heart.     Which  side  of 

91 


92 


ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 


the  heart  is  more  full}^  exposed  to  the  view  when  the  chest  is  opened? 
Palpate  with  the  tip  of  your  index-finger  the  walls  of  the  right  and  left 
ventricles,  observing  in  each  case  the  difference  in  the  texture  of  the 
cardiac  muscle  on  systole  and  diastole.  Also  note  the  much  greater 
thickness  of  the  left  musculature.  Observe  that  the  two  auricles  con- 
tract practically  simultaneously,  and  that  their  contraction  begins  near 
the  orifice  of  the  venae  cavse.  Likewise,  note  that  the  two  ventricles 
contract  together  as  soon  as  the  auricular  systole  has  been  completed. 
Expose  the  superior  and  inferior  cavse  and  observe  their  pulsations 
(venous  pulse).  Expose  the  aorta  and  pulmonary  artery  and  study  their 
pulsations  (arterial  pulse). 

Place  the  tip  of  your  index-finger  upon  the  surface  of  the  left  auricular 
appendix.  Press  downward.  Do  you  feel  the  flaps  of  the  mitral  valve 
hitting  against  your  finger?  Repeat  this  observation  on  the  opposite 
side.     Blow  a  spray  of  albulin  upon  the  heart  to  prevent  its  drying. 


Fig.  57. — Cardiometer. 
The  heart  is  inserted  through  a  perfora- 
tion in  rubber  membrane  (R)  into  cavity 
of  a  hemLspheric  plass  capsule  (C).  The 
latter  is  connected  with  a  recording  tam- 
bour (T). 


Fig.  58. — Clamp  for  Producing  Heart- 
block.     {After  Erlanger.) 


Discontinue  the  artificial  respiration  for  a  brief  period  of  time  until 
the  heart  has  been  markedly  slowed.  Again  study  the  progress  of  the 
wave  of  contraction  and  note  the  gradual  change  in  the  color  of  the 
heart.  Its  venosity  is  most  clearly  betrayed  by  the  left  auricle,  the 
color  of  which  gradually  changes  from  bright  red  to  dark  purple.  Ex- 
plain this  phenomenon.  Resume  artificial  respiration.  Allow  a  few 
drops  of  a  slightly  warmed  saline  solution  to  fall  upon  the  heart.  Note 
the  increase  in  its  frequency. 

Procure  a  small  cardiac  plethysmograph,  usually  consisting  of  a  hemi- 
spheric capsule  of  glass  the  orifice  of  which  has  been  closed  with  a  rubber 
membrane.  Incise  the  rubber  membrane  near  its  center,  and  push  the 
ventricular  portion  of  the  heart  through  this  opening  into  the  cardiom- 
eter.    Connect  the  tubular  outlet  of  the  latter  with  a  recording  drum 


THE    HEART  93 

and  ajiain  rogistor  tho  vohiniotric  clianuos  of  tho  lioart.  Ofolude  the 
veiui'  cavce  for  a  few  luorncnt.s.  Explain  tho  resuh.  Witluhiiw  the 
ventricles  from  the  cardiometer  and  allow  the  heart  to  recuperate.  If 
necessary,  cover  it  for  a  time  with  cotton  moistened  with  warmed  saline 
solution. 

Af^ain  record  the  volume-curve  of  the  ventricles.  Temporarily 
obstruct  the  arch  of  the  aorta.  lOxplain  the  result.  Allow  the  heart  to 
rest. 

2.  Heart-block.  Fibrillation.—  Procure  a  clamp  such  as  is  represented 
in  Fi<!;.  aS.  Hemove  the  loose  coimective  tissue  from  th(!  wall  of  the 
aorta  along  a  line  forming  the  right  edge  of  the  mass  of  fat  which  covers 
the  anterior  asjxH't  of  this  blood-vessel.  Set  the  point  of  the  hook  in 
this  place,  corresponding  to  the  tip  of  the  membranous  septum  of  the 
ventricles.  Direct  the  needle  ol)liquely  downward  and  toward  the 
limien  of  the  aorta  and  force  it  into  the  left  ventricle,  a[)proximately  at 
the  junction  of  the  right  and  posterior  flaps  of  the  mitral  valve.  Turn 
the  point  of  the  hook  backward,  so  that  the  short  arm  of  the  L-shaped 
clamp  comes  to  lie  parallel  to  the  ventricular  septum.  Now,  move  the 
bar  until  it  lies  parallel  to  the  first  part  of  the  arch  of  the  aorta  and 
force  the  short  arm  of  the  hook  into  the  septum  at  a  point  about  3  to 
6  mm.  below  the  auriculoventricular  junction  and  somewhat  posterior 
to  the  mesial  flap  of  the  mitral  valve.  Do  not  include  the  main  trunk 
of  the  coronary  artery  in  the  clamp.  Tighten  the  clamp  sufficiently 
to  cause  a  partial  block.  Not  every  auricular  contraction  will  then  be 
followed  b}'  a  ventricular  contraction.  This  condition  simulates  the 
condition  of  heart-block  in  man,  usually  brought  about  by  inflammatory 
lesions  along  the  course  of  the  bundle  of  His. 

If  done  in  an  improper  manner,  the  ventricle  will  immediately  be 
thrown  into  a  condition  of  fibrillation.  Its  musculature  then  executes 
irregular  wave-like  contractions.  This  condition  may  also  be  pro- 
duced b}^  injections  of  strophanthin  (about  0.0003  gram).  Shortly  before 
the  onset  of  the  fibrillation  the  heart  frequently  shows  a  typical  block. 


LESSON  XVII 

THE  HEART  (Concluded) 

PERCUSSION    AND    AUSCULTATION    OF    THE   HUMAN    HEART    UNDER 
DIFFERENT  CONDITIONS 

1.  The  Area  of  Cardiac  Dulness. — Percuss  the  region  of  the  heart 
of  the  subject,  beginning  in  each  case  well  without  the  bountlarios  of 
this  organ,  and  passing  radially  toward  the  sternal  articulation  of  the 
third  rib.  Accurately  note  the  point  where  the  deep  resonance  of  the 
lung  passes  over  into  the  area  of  dulness  of  the  heart.  Outline  the 
bounclaries  of  the  latter  with  colored  chalk.  What  is  its  size  and  posi- 
tion? How  is  this  area  changed  by  the  movements  of  the  lungs  on 
inspii-ation  and  expiration?  Explain.  If  abnormalities  in  its  size  are 
found,  give  probable  cause.    Outline  the  area  of  cardiac  flatness. 

Annotation. — Percussion  is  usually  practised  by  placing  the  middle  and  index- 
fingers  of  your  left  hand  flat  against  the  wall  of  the  chest.  Tap  upon  them  sharply 
with  the  index  and  middle  fingers  of  your  riglit  hand.  In  tapping,  the  right  hand 
should  he  held  lose  at  the  wrist,  and  the  second  and  third  phalanges  should  be  fle.xed 
upon  the  first  at  right  angles. 

2.  The  Rate  of  the  Heart. — Determine  by  auscultation  the  number 
of  the  heart-beats  of  the  subject  while  he  successively  assumes  the  re- 
cumbent, sitting,  and  standing  position.  Tabulate  the  results  and 
ascertain  the  differences.  Have  the  subject  make  forty  flexions  and 
extensions  of  the  arms  in  one  minute.  Again  determine  the  cardiac 
rate.  Repeat  the  count  after  the  subject  has  made  thirty  deep  knee 
bendings  in  one  minute,  and  again  after  a  stationary  run  lasting  one- 
half  minute.     Arrange  your  results  in  the  form  of  a  table. 

Determine  the  heart-rate  for  one  minute.  Ask  the  subject  to  swal- 
low.    What  difference  do  you  note?    , 

Determine  the  heart-rate.  Ask  the  subject  to  concentrate  his  atten- 
tion upon  his  heart.  Do  you  note  any  difference?  Ascertain  whether 
the  subject  is  able  to  increase  his  cardiac  rate  volitionally. 

Annotation. — The  method  of  auscultation  is  conveniently  practised  by  applying 
the  ear  to  the  chest  of  the  subject,  preferably  in  the  region  between  the  left  nip|)le 
and  the  sternum.  The  sounds  are  loudest  in  this  area.  .Since  we  are  dealing  in  the 
above  experiments  with  the  freciuency  of  the  heart,  you  may  allow  a  thin  garment 
to  intervene  between  your  ear  and  the  skin  of  the  subject. 

3.  The  Cardiac  Impulse  or  Apex-beat. — Carefully  observe  the  chest 
in  the  region  of  the  apex  of  the  heart,  i.  e.,  in  the  fifth  intercostal  space, 
and  at  a  distance  of  about  2  cm.  to  the  right  of  the  left  nipple.  Note 
the  periodic  protrusion  of  the  chest  wall.     jMark  the  location  of  this 

95 


96 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


impulse  with  a  blue  pencil.  Observe  the  changes  in  its  conspicuousness 
when  the  position  of  the  subject  is  changed  and  during  inspiration  and 
expiration.  Explain  the  results.  If  the  impulse  is  not  in  its  normal 
place,  ascertain  the  direction  and  degree  of  its  displacement.  Give  its 
probable  cause.  Palpate  the  radial  artery  and  note  the  interval  of  time 
between  the  radial  pulse  and  the  cardiac  impulse.  Palpate  the  carotid 
arterv  low  in  the  neck.     Note  that  the  difference  in  time  between  this 


Fig.  59. — Cardiograph. 
The  tape  is  strapped  around  the  chest.    The  central  button  is  applied  to  the  "apex- 
beat"  and  its  pressure  on  the  chest  wall  regulated  by  means  of  the  three  screws  at  the 
sides.     The  tube  at  the  upper  part  of  the  instrument  serves  to  connect  the  drum  of  the 
cardiograph  with  a  registering  tambour.     (Sanderson.) 

pulse  and  the  cardiac  impulse  is  much  less,  a  result  easily  explicable 
upon  the  ground  of  distance. 

Adjust  a  cardiograph  to  the  area  of  the  cardiac  impulse.  Connect 
it  with  a  recording  tambour  and  allow  the  latter  to  register  its  excursions 
upon  the  smoked  paper  of  a  kymograph  revolving  at  a  moderate  speed. 
This  record  should  be  made  above  a  time-curve,  registered  by  a  .laquet 
chronograph. 


Stc  I 


Fig.  60. — Cardiogram. 
AB,  Systole;  BC,  plateau;  CD,  diastole;  DA,  pause;  time  in  seconds. 

Explain  the  character  of  the  cardiogram  so  obtained.  Excepting 
the  cardiac  rate,  is  it  possible  to  derive  valuable  data  from  this  curve 
which  more  particularly  pertain  to  the  quality  of  the  contractions  of 
the  heart?     Give  reasons  for  your  conclusions. 

Annotation. — The  method  of  palpating  the  radial  artery  is  practised  as  follows: 
VVitli  your  left  hand  support  tlie  right  hand  of  the  subject  in  a  position  of  slight 
extension.     As  a  rule,  the  right  artery  gives  better  results.     Place  the  second  and 


THE    IIKAKT  97 

third  fiii^'fis  of  your  ri^lit  liaud  ui)oii  the  radial  artery  dose  to  the  wrist.  It  is  then 
a  simple  matter  to  deteriiiiue  the  frefiueiiey  of  tlie  pulse.  Hesides,  the  third  finger 
may  he  employed  to  (•om])ress  the  artery  and  the  second  to  palpate.  In  this  way  the 
experimenter  may  ol)tain  an  idea  re^'ardiu^;  the  tension  prevailing  in  the  vascular 
system  of  the  suhjeet. 

4.  The  Heart  Sounds. — Adjust  your  eai-  (lirtM'tiy  to  the  area  of  the 
apex-l)eat  of  the  suljjcct.  Study  the  (iiudity  and  intensity  of  the  car- 
diac sounds.  How  many  soiuids  do  you  heai?  Note  the  pause  fol- 
lowing the  second  sound.  Palpate  the  radial  pulse  and  determine 
whether  these  sounds  are  produced  during  ventricular  systole  or  diastole. 
Ascertain  precisely  when  they  occur  and  where  they  are  most  intense. 
Request  tlie  sul)ject  to  stop  respiring  after  a  deep  inspii'ation  and 
observe  the  lesser  audibility  of  these  .sounds.  State  the  reason  for  this 
change.  Ask  the  subject  to  cease  respiring  after  a  forced  expiration. 
Why  are  these  sounds  now  more  clearly  heard? 

Repeat  these  tests  with  the  help  of  a  stethoscope.  Place  its  chest- 
piece  over  different  regions  of  the  heart.  Compare  the  relative  in- 
tensity of  the  sounds  when  heard  at  the  apex  and  when  heard  over  the 
junction  of  the  second  right  costal  cartilage.  Do  you  obtain  a  dif- 
ference?    Give  reasons  for  it. 

Having  thoroughly  familiarized  yourself  with  the  character  of  the 
normal  heart  sounds,  study  a  simple  murmur,  such  as  may  arise  in  con- 
sequence of  mitral  stenosis  or  aortic  regurgitation.  Note  its  char- 
acter, point  of  greatest  intensity,  and  relation  to  the  cardiac  cycle. 
Also  familiarize  yourself  with  the  so-called  extracardiac  friction  sounds, 
hemic  murmurs,  and  arterial  and  venous  bruits. 

7 


LESSON  XVIII 

THE  CIRCULATION 

THE  CAPILLARY  CIRCULATION.     CONVERSION  OF  AN  INTERMITTENT 
INTO  A  CONSTANT  FLOW.     SCHEMA  OF  THE  CIRCULATION 

1.  The  Capillary  Circulation. — Procure  a  microscope  with  low-  and 
hifih-powor  ol)jo('tives,  a  thin  cork  board  about  20  cm.  Ions  and  10  cm. 
wide,  and  a  few  pins.  Bore  a  hole  al)out  1  cm.  in  diameter  dose  to 
the  margin  of  the  cork  board.  Pith  a  frog,  being  careful  not  to  lose 
any  blood.  Immediately  close  the  opening  with  the  pointed  end  of  a 
short  piece  of  wood.  Place  the  frog,  dorsum  turned  upward,  upon  the 
boaid  and  bring  one  foot  ovei'  the  hole  in  the  cork  board.  Stretch  the 
web  uniting  the  second  and  third  toes  across  the  opening,  and  hold  tiie 
toes  in  place  by  means  of  pins  or  threads.  Do  not  sti-etch  the  web 
unduly,  so  as  not  to  block  the  blood-vessels.  Adjust  the  body  of  the 
frog  in  an  easy  position. 

Fasten  the  cork  board  to  the  stage  of  the  microscope  and  illuminate 
the  web  under  an  objective  of  low  power.  Moisten  the  frog  repeatedly- 
with  saline  solution.  Observe  the  movement  of  the  blood  and  differ- 
entiate between  the  red  and  white  corpuscles.  Note  the  differences 
in  the  caliber  of  the  blood-vessels  and  the  speed  of  the  blood  flow. 
Ascertain  whether  a  certain  vessel  is  an  arteriole,  a  true  capillary, 
or  a  venule.  Select  a  true  capillary  and  observe  how  the  red  cells  force 
their  way  through  it,  elongating  if  necessary.  Find  a  capillary  which  is 
so  small  that  only  plasma  passes  through  it.  Do  you  observe  an  inter- 
mittency  in  the  flow  anywiiere  in  the  field?  What  is  its  probable  cause? 
Have  you  seen  a  reversion  of  the  blood  flow?     Give  its  cause. 

Carefully  adjust  the  high-power  objective  to  the  web,  and  repeat  the 
preceding  observations. 

2.  Intermittent,  Remittent,  and  Constant  Flow. — Procure  a  piece  of 
band-tubing  about  1.5  m.  in  length.  Insert  in  one  of  its  ends  a  glass 
cannula,  and  in  the  other  a  valved  rubber  syringe.  Dip  the  inlet  tube 
of  the  latter  in  a  basin  of  water  and  ask  the  assistanfto  hold  the  end  of 
the  band-tubing  over  the  sink. 

Compress  the  rubber  bulb  at  intervals  of  five  seconds.  Note  that 
the  tubing  fills  gradually,  but  does  not  discharge  until  it  has  attained 
a  definite  degree  of  distention.  It  then  discharges  a  certain  quantity 
of  water  with  every  compression  of  the  bulb  (intermittent  flow).  Com- 
press at  a  faster  rate  until  the  flow  does  not  cease  entirely  during  the 
interims  (remittent  flow).  Compress  at  still  briefer  intervals  until 
the  tubing  attains  a  high  degree  of  distention  and  continues  to  emptj' 
its  contents  evenly  during  the  time  when  the  rubber  bulb  aspirates 
(constant  flow).     Obviously,  the  successive  muscular  efforts  required  to 

99 


100 


ADVANCED    LESSONS   IN   PRACTICAL   PHYSIOLOGY 


compress  the  rubber  bulb  are  stored  in  the  wall  of  the  tubing  in  the 
form  of  elastic  tension.  As  soon  as  the  internal  pressure  is  lessened 
during  the  interims  this  elastic  power  acts  upon  the  water  within  the 
tubing  and  continues  to  force  it  onward  through  the  outlet.  To  ac- 
complish this  end  the  tubing  must  be  highly  distended,  i.  e.,  it  must  be 


Fig.  61.— Simple  Schema  to  Illustrate  the  Factors  Producing  a  Constant  Head 
OF  Pressure  in  the  Arterial  System. 
a,  A  syringe  bulb  with  valves,  representing  the  heart;  b,  glass  tube  with  fine  point 
representing  a  path  with  resistance  alone,  but  no  extensibility  (the  outflow  is  in  spurts 
synchronous  with  the  strokes  of  the  pump);  c,  outflow  with  resistance  and  also  extensible 
and  elastic  walls  represented  by  the  large  rubber  bag,  e,  the  outflow  is  a  steady  stream  due 
to  the  elastic  recoil  of  the  distended  bag,  e.     (Howell.); 

retained  in  a  condition  of  hyperfilling.  To  what  constituents  of  the 
vascular  system  may  the  different  parts  of  this  apparatus  be  compared? 
Remove  the  narrow  glass  cannula  (capillaries)  from  the  end  of  the 
band-tubing  (arteries).  This  decreases  the  peripheral  resistance.  What 
effects  do  you  observe?  Insert  a  narrow  glass  cannula  and  note  the 
effects  of  this  increase  in  the  peripheral  resistance  upon  the  distention 


Fig 


Artificial  Schema  of  the  Circulation.     (Porter.) 


of  the  band-tubing  and  the  escape  of  water.  In  the  latter  case  you  may 
materially  decrease  the  number  of  the  compressions  without  destroying 
the  constancy  of  the  flow. 

3.  Schema  of  the  Circulation. — The  basin  of  water  represents  the 
left  auricle,  tlie  rubber  bulb  the  left  ventricle,  and  the  large  rubber  tube 
the  aorta.     The  large  glass  tube  next  to  the  basin  contains  the  mitral 


THE   CIRCULATION 


101 


valvo,  and  the  one  distallj'  to  the  hiilh  the  aortic  semilunar  valve.  The 
side  ijranc'h  from  the  ventricle  maj'  Ik;  connected  by  means  of  a  thistle 
tul)e  with  a  membrane  manometer,  and  may  thus  be  used  to  register 
the  chanjies  in  pressure  in  the  ventricle.  In  a  similar  manner  the 
clianges  in  pressure  in  the  aorta  may  be  recorded  (aiteiial  i)ulse). 
Beyond  the  aorta  lies  the  remaining  porti(Mi  of  the  arterial  system,  to 
which  there  is  attached  a  mercury  manometer  for  measui-ing  the  arterial 
pressure.  Into  the  dish  opens  the  venous  system.  It  is  equipped  with 
a  mercury  manometei-  for  measuiing  the  venous  picssure.  Between 
the  arteries  and  veins  are  the  capillaries,  represented  in  the  schema  bj' 
a  short  piece  of  porous  bamboo,  and  a  side  branch  bearing  a  clamp. 


Fig.  63. — More  Recent  Schema  of  the  Circulation. 
The  action  of  the  heart  is  here  imitated  by  a  tamljour,  rhythniically  compressed  by 
hand.     The  veins  empty  tfieir  contents  into  a  receptacle  (right  auricle)  fastened  to  the 
side  of  the  upright  stand.     (Harvard  Apixiratus  Co.) 


A.  Normal  Circulation. — Dip  the  inlet  and  outlet  tubes  of  this 
system  into  the  water  in  the  basin  and  pmnp  gently  with  the  rubber 
bulb  until  the  different  tubes  have  been  filled  with  water.  Clamp  the 
side  branch  between  the  arteries  and  veins.  Pump  gently  at  the  rate 
of  about  sixty  times  in  a  minute,  and  observe  the  following: 

(a)  The  action  of  the  valves, 

(6)  The  arterial  pressure  and  its  changes, 

(c)  The  venous  pressure, 

(d)  The  pulse  in  the  aorta,  and 

(e)  The  character  of  the  flow  from  the  veins. 

Open  the  clamp  slightly,  so  as  to  simulate  dilatation  of  the  arterioles, 
and  pump  as  before.  What  is  the  effect  of  this  procedure  on  the  arterial 
and  venous  pressures  and  on  the  character  of  the  venous  flow? 


102         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

Open  the  clamp  widel}',  and  pump  at  the  rate  of  about  twelve  times 
in  a  minute.     Effect? 

Determine  the  respective  conditions  under  which  the  venous  flow 
becomes  intermittent,  remittent,  and  constant. 

Try  to  discover  the  causes,  in  the  normal  circulation  of  the  blood, 
of  the  great  difference  between  the  arterial  and  venous  pressures,  and 
the  absence  of  a  pulse  in  the  veins. 

B.  Intrwentricular  Pressure. — Place  a  thistle  tube  against  the  mem- 
brane closing  the  lateral  tube  of  the  rubber  bulb  (ventricle)  and  con- 
nect it  with  a  recording  drum.  Register  the  changes  in  pressure  occur- 
ring within  the  ventricle  upon  the  smoked  paper  of  a  slowly  revolving 
kjmiograph. 

C.  Pulse. — Place  the  thistle  tube  upon  the  ''aorta"  and  register  its 
pulsations. 

D.  Mitral  Insuffidencij. — Remove  the  rubber  sheath  from  the  glass 
tube  representing  the  mitral  valve.  This  produces  a  condition  analogous 
to  mitral  insufficiency.  Pump  at  a  normal  rate.  Observe  the  effect 
of  this  lesion  upon  the  intraventricular  pressure,  the  arterial  pressure, 
the  aortic  pulse,  and  the  venous  discharge.     Replace  the  sheath. 

E.  Mitral  Stenosis. — Tie  a  thread  around  the  sheath  of  the  mitral 
valve,  thereby  restricting  the  size  of  this  opening.  This  produces  a 
condition  analogous  to  mitral  stenosis.     What  effects  do  you  notice? 

F.  Aortic  Insufficiency. — Remove  the  sheath  from  the  semilunar 
valve,  producing  thereby  a  condition  analogous  to  aortic  insufficiency. 
What  changes  do  you  observe?     Replace  the  sheath. 

G.  Aortic  Stenosis. — Tie  a  thread  around  the  sheath  of  the  semilunar 
valve  so  that  the  opening  becomes  smaller.  This  condition  simulates 
aortic  stenosis.     Observe  the  results. 


LE880N  XIX 

THE  CIRCULATION  (Continued) 

THE    CAUSE    AND    VELOCITY   OF  THE  PULSE.      DIRECT  METHOD  OF 
ASCERTAINING  THE  BLOOD-PRESSURE 

1.  Schema  Illustrating  the  Differences  in  the  Velocity  of  the  Blood 
Flow. — Procure  :i  glass  bull),  such  as  is  rcprosontod  in  Fig.  {'A.  Con- 
nect its  inlet  tube  by  means  of  a  relatively  narrow  glass  tube  with  the 
water  hydrant.  On  opening  the  stop-cock  the 
water  will  advance  to  a  higher  level,  its  flow 
being  most  rapid  in  the  narrow  inlet  tube,  very 
slow  in  the  enlarged  central  portion,  and  inter- 
mediate in  the  outlet  tube.  If  all  the  arteries, 
capillaries,  and  veins  could  be  united  into  single 
tubes,  the  calibers  of  these  three  divisions  would 
differ  in  the  same  way,  i.  e.,  the  bed  formed  by 
the  arteries  would  be  the  smallest  of  all,  and 
that  of  the  capillaries  the  largest.  Since  the 
speed  of  flow  is  inversely  proportional  to  the 
lumen  of  the  vessel,  the  blood  must  attain  its 
greatest  velocity  in  the  arteries,  and  its  slightest 
velocity  in  the  capillaries. 

2.  Schema  Illustrating  the  Cause  and  Velocity 
of  the  Pulse. — Procure  four  glass  tubes,  each 
about  1  m.  in  length  and  1  cm.  in  diameter. 
Arrange  them  vertically  about  20  cm.  apart, 
and  connect  them  in  series  b}^  means  of  band- 
tubing,  each  piece  being  about  50  cm.  in  length. 
Attach  a  valved  rubber  bulb  to  the  end  of  this 
system,  and  allow  its  inlet  tube  to  dip  into 
a  basin  filled  with  water.  Compress  the  bulb 
rhythmically  until  this  entire  system  has  been  well  filled.  The  water 
then  rises  in  the  laterals  to  a  certain  level,  indicating  the  pressure  ex- 
isting at  these  different  points.  Secondly,  each  compression  of  the  bulb 
then  produces  an  oscillation  of  the  water  in  the  successive  laterals,  the 
water  in  the  lateral  nearest  the  rubber  bulb  being  moved  first  (Fig.  65). 

3.  The  Direct  Method  of  Determining  the  Arterial  Blood-pressure. 
— Weigh  the  animal  and  compute  the  quantity  of  blood  present  in  its 
body.  Give  it  ether  and  maintain  the  anesthesia  until  it  has  been  killed. 
Perform  tracheotomy.  Expose  the  carotid  artery  on  the  left  side  and 
the  external  jugular  vein  on  the  right  side.  (See  Lesson  X.)  Place  a 
silk  thread  loosely  around  each  blood-vessel.  Raise  both  sufficiently  to 
occlude  them.     Notice  that  the  artery  is  more  highly  distended  on  the 

103 


Fig.     64. — Schema 
Illustrating  the  Dif- 
ference IN  the  Veloc- 
ity OF  the  Blood  Flow. 
A,  Arteries;  C,  cap- 
illaries; V,  veins. 


104 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


central  side  of  the  ligature,  and  that  its  distal  end  does  not  collapse 
altogether,  owing  to  the  fact  that  the  carotid  arteries  anastomose  rather 
freely  with  one  another.  Observe  that  the  distal  end  of  the  vein  is 
highly  distended,  whereas  its  central  end  is  collapsed.  This  is  one  of 
the  tests  which  Harvey  employed  to  prove  the  circulation  of  the  blood. 
Observe  the  changes  in  the  caliber  of  the  vein  during  inspiration 
and  expii-ation.  During  the  former  period  its  size  is  decreased,  and 
during  the  latter,  increased.  These  changes  are  referable  to  the  aspira- 
tory  action  of  the  thorax,  because  the  inspiratory  movement  augments 
the  elastic  pull  of  the  lung  tissue  upon  the  yielding  walls  of  the  central 
venous  trunks.  During  expiration,  on  the  other  hand,  the  lung  tissue 
recoils  more  completely,  and  does  not  exert  so  powerful  a  traction  upon 
the  venous  trunks  and  their  contents.  Accordingly,  the  inspiratory 
movement  decreases  the  pressure  in  the  central  veins  and  draws  a 
larger  quantity  of  blood  into  them  and  the  right  side  of  the  heart. 


Fig.  65. — Schema  Illustrating  the  Cause  and  Velocity  of  the  Arterial  Pulse. 
W,  Basin  with  water;  P,  valved  rubber  bulb;  B,  band-tubing  between  the  laterals  C. 


Observe  the  changes  in  the  caliber  of  the  artery  during  inspiration 
and  expiration.  It  increases  during  the  former  period,  and  decreases 
during  the  latter.  Since  the  heart  receives  a  larger  quantity  of  blood 
during  inspiration,  it  is  capable  of  transferring  a  larger  amount  of  it 
into  the  arteries.  The  pulmonary  blood-vessels  are  at  this  time  more 
widely  dilated,  and  permit  a  free  through  flow. 

Free  the  common  carotid  artery  from  its  fascia  and  insert  in  it  a 
glass  cannula.  Fill  the  latter  with  a  solution  of  sodium  carbonate. 
Fill  the  rubber  tubing  and  central  limb  of  the  mercury  manometer  with 
the  same  solution.  Determine  the  zero-line  or  line  of  atmospheric 
pressure  (760  mm.  Hg.).  Connect  the  arterial  cannula  with  the  man- 
ometer. 

Annotation. — ^The  zero-line  is  ascertained  as  follows:  Bring  the  level  of  the  mer- 
cury in  the  central  limb  of  the  manometer  on  the  same  level  with  the  carotid  artery. 
Connect  the  rubber  tubing  with  a  glass  bulb  filled  half-way  with  a  solution  of  sodium 
carbonate.  Adjust  the  level  of  this  solution  to  the  level  of  the  mercury  in  the 
central  limb  of  the  manometer.     At  this  time  the  recording  needle  of  the  float, 


THE    t'lmiLATION 


105 


resting  upon  the  mercun-  in  the  tiistal  limb  of  the  manometer,  is  set  at  zero.     In 
order  to  be  iil)le  to  retain  this  Hne  during  the  suereethng  experiments,  adjust  the  sta- 


FiG.  66. — Schema  to  Show  the  Connection  Made  Between  the  Artery  and  Man- 
ometer. 
M,  Manometer;  H,  mercurial  column;  F,  float;  D,  recording  needle;  K,  kymograph; 
B.  tube  Icadinc;  to  reservoir  filled  with  solution  of  sodium  carbonate;  K,  rubber  tubing 
filled  with  sodiimi  carbonate  solution;  C,  glass  cannula  in  artery;  A,  clip  upon  artery; 
V,  maximal-minimal  valve  (Frank)  to  be  inserted  in  this  circuit;  1,  maximal,  2,  minimal 
side;  Vi,  maximal  valve  of  Hurthle.  A  minimal  valve  is  obtained  by  inverting  the  central 
tube. 


Fig.   67. — Diagram  to  Show  the   Adjustments  Necessary   for   Determining  the 

Zero-line  of  the  Manometer  (M). 

Its  central  limb  (A)  is  brought  upon  the  same  horizontal  line  as  the  level  of  the  water  in 

the  glass  bulb  (B)  when  held  at  the  level  of  the  blood-vessel  (C). 


tionary  recording  lever  of  the  manometer  to  the  level  of  the  writing  needle  of  the 
float.     The  latter  may  then  rise  above  this  zero-line  to  indicate  the  blood-pressure. 


106         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

The  recording  needle  of  the  manometer  having  been  placed  against 
the  smoked  paper  of  the  kymograph,  allow  a  small  quantity  of  sodium 


Fig.  68. — Record  of  Blood-pressure  Showing  the  Cardiac  and  Respiratory  Varia- 
tions. 
The  time,  registered  in  seconds,  serves  as  the  abscissa. 

carbonate  to  enter  the  connecting  tubes  from  a  receptacle  suspended 
above  the  manometer.     Remove  the  chp  from  the  artery,  and  adjust 


Fig.  69. — Tr.\ube-Herixg  Curves. 
The  time  is  given  in  .seconds.     The  smallest  pulsations  represent  the  cardiac  varia- 
tions,  those  of  intermediate  size  the  respiratory  variations,  and  the  large  waves  the 
Traube-Hering  variations. 

the  speed  of  the  drum  so  as  to  render  the  individual  cardiac  variations 
clearly  perceptible.     Observe  the  character  of  the  respiratory  varia- 


THK    CIHCrLATIOX  107 

tioiis  ill  prossuro  and  uoto  that  (>acli  is  ina(l(>  ui)  of  a  nuinl)or  of  cardiac 
variations.  Does  the  tracinj^  show  Traubc-Horin^  curves,  which  are 
rhythmic  waves  including  several  respiratory  variations?  Ascertain  the 
height  of  the  j:)ressurc. 

Aniiotdtidii.  It  is  lu'st  to  establisl)  a  certain  (leRroe  of  pressure  in  the  manometer 
before  the  Ijlood  is  actually  allowed  to  act  aj;ainst  tlie  mercury.  In  a  cat  or  dog  we 
may  expect  to  obtain  a  pressure  efiuallinj;  120  to  KIO  mm.  Hj;.  Thus,  if  we  estab- 
lish a  pressure  of  UK)  nun.  H^;.  beforeliand,  only  a  small  (pumtity  of  1)1o<h1  need  pa.ss 
into  the  glass  cannula  to  i)r(Kiuce  the  additional  pressure.  On  the  otlier  hand,  if 
the  recording  -needle  is  allowed  to  ren)ain  at  zero  to  begin  with,  the  aforesaid 
degree  of  pressure  can  only  be  pnMluced  by  the  passage  of  a  considerable  portion  of 
the  blood  into  the  comiecting  tubes.  In  small  aninuils  this  would  give  rise  to  a 
material  decrease  in  pressure,  and  would  greatly  favor  the  occurrence  of  coagulation 
in  the  connecting  tube. 

To  obtain  the  bkxxl-pressure,  measure  the  distance  between  the  zero-line  and 
the  midline  of  the  oscillations  recorded  by  the  manometer  (H).    Employ  the  fornmla: 

P  =  2H  —    "- 

13.5 

Obviously,  the  recording  needle  registers  merely  the  upward  movement  of  the 
mercury  in  the  distal  limb  of  the  manometer.  It  must  lie  remembered,  however, 
that  the  mercury  in  the  central  limb  moves  at  this  time  an  ecpial  distance  in  a  down- 
ward direction,  ami  hence  the  distance  between  the  zero-line  and  the  oscillations  in 

pressure,  as  registered  by  the  needle,  must  be  niultij)lied  by  2.     In  addition,  the  cor- 
u 

rection  must  be  made,  because  the  blood  acts  against  mercury,  which  is  13.5 

13.5 

times  as  heavy  as  water. 

In  order  to  obtain  a  more  accurate  mean  pressure  a  large  munber  of  measure- 
nfents  must  be  made,  first,  of  the  systolic  pressure,  and  secondly,  of  the  diastolic 
pressure.  The  arithmetic  mean  between  the  averages  of  these  jjressures  may  be 
taken  to  be  the  mean  blood-pressure.  More  acciu-ate  determinations  require  piano- 
metric  measurements. 

4.  Influence  of  Posture. — Remove  the  clip  from  the  artery,  and 
again  record  tlio  blood-pressure.  Raise  the  posterior  extremities  of  the 
animal  vertically  upward.  Keep  them  in  this  position  for  ten  seconds 
and  again  lower  them  slowly.  By  this  means  a  large  quantity  of  blood 
is  forced  into  the  head-circuit  of  the  animal,  occasioning  a  rise  in  the 
carotid  pressure.  Such  increases  in  blood-pressure  are  usually  asso- 
ciated with  a  reflex  •slowing  of  the  heart. 

5.  Compression  of  the  Abdominal  Aorta. — The  preceding  result  may 
also  be  obtained  by  temporarily  occluding  important  subdivisions  of 
the  vascular  system.  Thus,  if  the  thuml)  is  pressed  flat  against  the 
spinal  column  somewhat  below  the  left  costal  arch  of  the  animal,  the 
resultant  comprcsssion  of  the  abdominal  aorta  must  lead  to  an  engorge- 
ment of  the  head-circuit  and  a  corresponding  rise  in  the  carotid  pressure. 
Observe  that  the  sudden  release  of  the  compression  usually  causes  the 
]iressure  to  fall  below  normal,  and  that  several  seconds  then  commonly 
elapse  before  it  again  assumes  its  normal  height.  It  is  only  natural 
to  assume  that  the  sudden  inrush  of  the  blood  into  the  previously  empty 


108         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

blood-vessels  of  the  posterior  part  of  the  body  must  cause  a  temporary- 
reduction  in  the  quantitj'  of  the  blood  allotted  to  the  head-circuit. 

6,  Influence  of  Hemorrhage. — Insert  a  cannula  in  the  femoral  artery. 
While  a  tracing  of  the  carotid  pressure  is  being  recorded  remove  the  clip 
from  the  femoral  artery  and  allow  20  c.c.  of  blood  to  escape  into  a  beaker. 
Observe  the  sj^stolic  increase  in  the  force  of  the  ejection.  Again  apply 
the  clamp  and  allow  the  pressure  to  adjust  itself.  What  factors  are 
involved  in  this  compensation?  Again  withdraw  20  c.c.  of  blood,  and 
continue  this  procedure  until  the  pressure  has  fallen  to  zero.  Care- 
fully observe  the  sjTiiptoms  of  excessive  hemorrhage,  as  displayed  by  the 
changes  in  the  character  of  the  respiratory  movements  and  the  rate  and 
force  of  the  heart.  How  much  blood  has  been  withdrawn,  and  what 
proportion  of  the  total  quantity  present  in  this  animal?  Kill  the  ani- 
mal by  giving  an  excessive  amount  of  ether. 


LESSON  XX 

THE  CIRCULATION  (Continued) 

VENOUS  VALVES.    INFLUENCE  OF  DYSPNEA  UPON  THE  BLOOD-PRESS- 
URE.   ACTION  OF  AMYL  NITRITE  AND  ADRENALIN.    HEMORRHAGE 

L  Position  and  Function  of  the  Venous  Valves.— Ask  the  subject 
to  hold  his  arm  in  a  dependent  position.  Encircle  the  forearm  with  a 
piece  of  rubber  tul)inf>;,  but  not  too  tightly.  Raise  the  arm.  Note 
the  distended  condition  of  the  veins  upon  the  dorsal  aspect  of  the 
hand.  Select  the  point  of  confluency  of  two  veins.  With  the  tip  of 
the  index-finger  of  your  left  hand  occlude  one  branch  tlistally  to  this 
point.  With  the  tip  of  the  index-finger  of  your  right  hand  brush  along 
this  vein  in  a  direction  from  periphery  to  center,  emptying  the  blood 
into  the  collecting  vein.  Observe  that  the  vein  so  emptied  does  not 
fill  again  until  you  have  removed  the  distal  finger  and  have  allowed  a 


Fig.  70. — Record  of  the  Carotid  Blood-pressure  Dirinc;  Dyspxea  (Dog). 
At  L  the  tracheal  tube  was  hold  shut  until  the  blood-pressure  bepan  to  drop. 

certain  quantity  of  blood  to  flow  into  it  from  its  tributaries.  More- 
over, while  emptied  a  marked  prominence  is  developed  at  its  point  of 
confluency  with  the  larger  vein,  indicating  the  position  of  the  valve 
guarding  its  central  orifice.  This  experiment  was  employed  by  Harvey 
to  prove  the  circulation  of  the  blood.  Examine  a  preparation  of  a 
segment  of  vein  preservcfl  in  alcohol. 

2.  Blood-pressure.  Influence  of  Dyspnea. — Anesthetize  a  mammal 
and  maintain  the  anesthesia  until  it  has  l)een  killed.  Perform  trache- 
otomy. Insert  a  cannula  in  the  carotid  artery  and  connect  it  with  the 
mercury  manometer.     Record  the  blood-pressure  upon  a  slowly  revolv- 

109 


110         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

ing  drum.  Occlude  the  tracheal  cannula  with  the  tip  of  your  finger. 
Observe  that  the  respii'atory  movements  gradually  assume  a  labored 
character  and  that  the  respiratory  variations  in  blood-pressure  are 
therebj^  rendered  more  conspicuous.  The  blood-pressure  rises  grad- 
ually. The  frequency  of  the  heart,  which  is  increased  at  first,  is  soon 
lessened.  The  heart  then  assumes  a  markedly  diastolic  character  and 
causes  the  blood-pressure  to  fall.  Immediately  remove  your  finger  from 
the  tracheal  cannula  and  wait  until  normal  hemodynamic  conditions 
have  again  been  established.  What  factors  are  involved  in  the  initial 
rise  in  blood-pressure? 

3.  Effect  of  Amyl  Nitrite. — Place  a  glass  bead  filled  with  amyl 
nitrite  in  a  small  glass  bottle.  Break  it  between  the  tongs  of  an  artery 
forceps.  Place  the  palm  of  your  hand  over  the  mouth  of  the  bottle. 
Record  the  blood-pressure  upon  a  slowly  revolving  drum.  Allow  the 
animal  to  inhale  the  amyl  nitrite  by  holding  the  end  of  the  rubber  tube 
attached  to  the  tracheal  cannula  in  the  bottle.  Remove  the  tube  from 
the  bottle  as  soon  as  the  blood-pressure  begins  to  fall.     Naturally,  the 


Fig.  71. — Effect  of  Amyl  Nitrite  on  Blood-pressure  (Dog). 

pressure  will  continue  to  drop  even  after  this  time  until  the  amyl 
nitrite,  which  has  been  absorbed  from  the  inspiratory  air,  has  been 
rendered  inert.  Subsequent  to  this  point,  however,  it  will  rise  slowly 
until  normal  conditions  have  again  been  estabhshed.  Explain  in  detail 
the  action  of  this  agent. 

What  are  the  hemodynamic  conditions  established  during  attacks 
of  angina  pectoris?  What  changes  may  be  effected  during  these  attacks 
by  inhalations  of  amyl  nitrite? 

Replace  the  clip  upon  the  artery  after  each  experiment.  If  coagula- 
tion has  set  in,  flush  out  the  tubing  as  well  as  the  cannula  with  sodium 
carbonate  solution. 

4.  Effect  of  Adrenalin. — Add  1  c.c.  of  adrenahn  (solution  1  :  1000) 
to  10  c.c.  of  saline  solution.  Expose  the  right  external  jugular  vein. 
Place  a  clip  upon  it  centrally  and  insert  a  cannula  distally  to  the  clip 
(toward  the  heart).  Fill  the  cannula  with  normal  saline  solution  and 
connect  it  by  means  of  a  short  piece  of  rubber  tubing  with  a  pipet 
containing  the  aforesaid  solution  of  adrenalin.     Fasten  the  pipet  in  a 


THE    CIIiCULATION 


111 


stand  obliquely  ahov'O  the  vein.  Keconl  the  hloofl-pressure.  Release 
tiie  clip  slightly  and  allow  1  to  2  c.e.  of  the  solution  of  achcnalin  to  enter 
the  venous  circulation.  Make  a  mark  upon  the  paper,  indicating  the 
moment  when  the  injection  was  made. 

Determine  the  length  of  the  latent  period  intervening  between  the 
injection  and  the  rise  in  blood-picssuic.  Account  for  this  interval. 
Note  the  character  of  the  react i<jn  and  explain  its  cause. 

What  is  the  effect  of  adrenalin  when  applied  to  bleeding  surfaces? 
State  why  adrenalin  is  added  to  solutions  used  for  purposes  of  infusion 
after  hemorrhage. 


Fig.  72. — Effect  of  Adrenalin  on  Blood-pressure  (Dog). 

Annotation. — Since  adrenalin  deteriorates  on  standing,  and  especially  when 
exposed  to  light,  its  strength  can  only  be  determined  in  a  physiologic  way.  Conse- 
quently, adjust  the  dose  to  the  reaction  obtained,  /.  c,  give  it  in  smaller  quantities 
if  the  rise  is  excessive  and  if  the  heart-beats  assume  a  pronouncedly  diastolic  char- 
acter. 1 


5.  Hemorrhage  and  Saline  Injection. — Heat  a  considerable  quantity 
of  physiologic  salt  solution  to  38°  C.  Draw  100  c.c.  of  this  solution  into 
a  pipet  and  connect  the  latter  with  the  cannula  in  the  jugular  vein. 
Record  the  blood-pressure.  Bleed  the  animal  through  the  femoral  ar- 
tery until  the  carotid  pressure  has  fallen  to  about  50  mm.  Hg.  Allow 
50  c.c.  of  saline  solution  to  enter  the  venous  circulation.  What  effect 
is  produced  thereby?  Repeat  the  injection  until  the  pressure  has  be- 
come normal.  How  large  an  amount  of  the  solution  has  been  injected? 
Kill  the  animal  by  giving  an  excessive  amount  of  ether. 


LESSON  XXI 
THE  CIRCULATION  (Continued) 

THE  EFFECT  OF  DIVISION  AND  STIMULATION  OF  THE  VAGUS  NERVE 
UPON  THE  BLOOD-PRESSURE  AND  ACTION  OF  THE  HEART 

1.  Stimulation  of  the  Intact  Vagi  Nerves.—  Ktliorizo  a  iiiainnial  and 
continue  th(^  aiicsthesia  until  tlie  animal  has  been  killed  at  the  end  of 
the  followinj^  expeiiineiits:  Perform  tracheotomy.  Listen  to  the  heart 
sounds  and  locate  the  cardiac  impulse.  With  the  tips  of  your  index- 
fingers  press  gently  upon  the  skin  of  the  neck  overlying  the  vagi  nerves. 
Do  you  notice  a  reduction  in  the  rate  of  the  heart?  Expose  the  com- 
mon carotid  artery  on  the  left  side  and  insert  in  it  a  straight  cannula 
to  be  connected  later  on  with  the  mercury  manometer.     Also  expose  the 


Fig.  73. — Record  of  Carotid  Blood-pressure. 

5,  Stimulation  of  left  vagus  nerve.     The  fall   in  prcs.sure  is  follDwed  by  compensatory 

changes  before  the  normal  pressure  is  again  estal^lished. 

common  carotid  artery  on  the  right  side,  and  separate  both  vagi  nerves 
from  the  sheaths  of  these  blood-vessels.  Place  each  in  a  loose  silk 
ligature.  Arrange  the  stimulating  apparatus  to  yield  a  quickly  inter- 
rupted current  of  medium  strength. 

Apply  the  electrodes  to  the  left  intact  vagus  and  stimulate  briefly, 
while  the  normal  blood-pressure  is  being  recorded.  In  case  tiie  effect 
is  too  indefinite,  increase  the  strength  of  the  current  shghtly.  Test 
the  opposite  nerve  in  the  same  manner  and  with  the  same  strength  of 
current.  Do  you  notice  a  difference  in  the  inhibitor  power  of  these 
nerves?     In  each  case  allow  the  pressure  to  return  to  normal  before  you 

8  113 


114  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

stimulate  again.     Note  the  compensatory  variations  occurring  at  this 
time. 

2.  Division  of  One  Vagus  Nerve. — Apply  another  loose  ligature  to 
each  vagus  nerve.  Record  the  normal  blood-pressure.  Ligate  one 
vagus  twice  and  cut  between  the  ligatures,  so  that  its  central  and  distal 
stumps  may  be  stimulated  separately.  Indicate  the  moment  of  the 
division  upon  the  tracing.  What  changes  do  you  observe  in  the  blood- 
pressure?  Obtain  the  cardiac  frequency  from  the  tracing  before  and 
after  the  section.     To  what  factor  do  you  attribute  the  rise  in  pressure? 

Stimulate  the  distal  end  of  this  nerve.  After  the  pressure  has  re- 
turned to  normal  stimulate  the  central  end  of  this  nerve.  What  deduc- 
tions may  be  drawn  regarding  the  inhibitor  qualities  of  the  vagi? 

Annotation. — It  has  been  stated  above  that  the  inhibitor  power  of  the  vagi 
nerves  differs  in  different  animals.  Thus,  cardio-inhibition  is  easily  obtained  in 
the  dog,  but  only  with  difficulty  in  cats.  Secondly,  in  certain  animals  the  stimulation 
of  the  central  end  of  one  vagus — the  other  being  intact — produces  a  reflex  slowing 
of  the  heart. 

3.  Division  of  Both  Vagi  Nerves. — Record  the  blood-pressure  and 
divide  the  opposite  vagus  in  the  same  manner.  Determine  the  cardiac 
rate  before  and  after  the  section.  Are  the  effects  previously  noted  now 
more  pronounced?  Stimulate  the  distal  and  central  ends  of  this  nerve. 
Compare  the  inhibitory  power  of  the  left  nerve  with  that  of  the  right. 

Annoiation. — The  inhibitor  power  of  these  nerves  varies  considerably.  Some- 
times the  left  and  sometimes  the  right  nerve  is  the  stronger  of  the  two,  but  most 
generally  the  right.  With  both  nerves  divided,  the  stimulation  of  either  central  end 
must  necessarily  fail  to  produce  a  reflex  slowing  of  the  heart. 

4.  Inhibition  of  the  Exposed  Heart.^ — Test  the  artificial  respiration 
apparatus  and  adjust  the  check-valve  for  an  air  current  of  medium 
volume.  Connect  the  tracheal  cannula  of  the  animal  with  the  ether- 
bottle.  Incise  the  skin  over  the  sternum.  By  means  of  a  pair  of 
strong  scissors  cut  through  this  bone  directly  in  the  median  Hne,  avoid- 
ing the  mammary  arteries.  Institute  artificial  respiration.  Vary  the 
position  of  the  stop-cock  upon  the  inlet  tube  to  give  to  the  lungs  a  normal 
degree  of  inflation.  Stop  the  bleeding  by  applying  a  compress  or  by 
torsion  and  ligation  of  the  vessels.  Pull  the  edges  of  the  sternum  apart 
by  means  of  a  strong  string  drawn  around  the  board.  Open  the  peri- 
cardial sac  and  inspect  the  heart,  repeating  the  observations  made 
in  the  course  of  Lesson  XVI.  Stimulate  the  distal  end  of  either  vagus 
nerve.  Note  that  the  heart  stops  in  diastole,  greatly  distended  by 
blood.  Observe  the  swollen  condition  of  the  central  veins,  indicating  a 
rise  in  venous  pressure. 

Endeavor  to  retain  the  heart  in  the  inhibited  condition  by  prolong- 
ing the  duration  of  the  stimulation.  What  happens?  When  the  heart 
resumes  its  beat  it  is  apparent  that  it  contracts  first  in  the  region  of  the 
pace-maker,  giving  a  well-marked  contraction  wave. 


THE    CIRCULATION 


115 


5.  Intracardiac  Pressure.—  Expose  tlio  ri{j;ht  oxtornal  jugular  vein. 
Place  II  clip  upon  it  centrally  and  ligale  it  about  2  cm.  farther  distally. 
Open  this  vein  between  the  clip  and  the  ligature  and  insert  the  end  of  a 
long,  hollow  probe  filled  with  physiologic  salt  solution.  Place  a  liga- 
ture rather  loosely  around  that  portic^n  of  the  vein  which  contains  the 
end  of  the  catheter.  Connect  the  latter  with  a  membrane  manometer. 
Remove  the  clip  from  the  vein  and  push  the  catheter  slowly  downward 
until  its  free  end  comes  to  lie  in  the  right  auricular  cavity.  Obtain  a 
tracing  of  the  right  intra-auricular  pressure. 

Push  the  catheter  through  the  auriculoventricular  orifice  into  the 
right  ventricle,  taking  care  not  to  injure  the  tricuspid  valve.  Obtain 
a  tracing  of  the  right  intraventricular  pressure.  Withdraw  the  catheter 
and  replace  the  clip  upon  the  vein. 


y^v^r--^ 


ta 


^     T 


'r-...-.U-:i^ 


Fig.  74. — Diagram  of  Membr-we  Manometer. 

M,  Rublaer  membrane  connected  with  writing  lever  (L).   The  drum  (7^  is  connected  with 

the  cannula  in  the  blood-vessel;  R,  rod  to  fasten  manometer  to  stand. 


Study  the  character  of  each  tracing  and  compare  them  with  one 
another.  Calculate  the  pressures  so  obtained  by  comparing  the  oscilla- 
tions of  the  membrane  with  those  of  a  mercury  manometer. 

6.  Entrance  of  Air  Into  the  Circulation. — Insert  a  glass  cannula  in 
the  right  external  jugular  vein.  Record  the  blood-pressure,  and  apply 
a  stethoscope  to  the  chest  wall.  Force  a  small  amount  of  air  into  the 
aforesaid  vein.  After  a  short  latent  period  the  blood-pressure  will  begin 
to  fall,  this  fall  being  accompanied  by  a  peculiar  noise  produced  by  the 
frothing  of  the  blood  within  the  heart,  as  the  valve  flaps  beat  against 
the  bubbles  of  air. 

Kill  the  animal  by  an  overdose  of  ether.  Open  the  heart  and  ex- 
amine the  character  of  the  blood.  Dissect  the  heart,  repeating  the 
observations  made  in  the  course  of  Lesson  XV. 


LESSON  XXII 

THE  CIRCULATION  (Continued) 

THE  VASOMOTOR  ACTION  OF  THE  CERVICAL  SYMPATHETIC, 
DEPRESSOR,  AND  SCIATIC  NERVES 

1.  The  Cervical  Sympathetic  Nerve. —  Etherize  a  rabbit  and  main- 
tain the  anesthesia  throughout  the  following  experiments:  Perform 
tracheotomy.  Make  an  incision  along  the  inner  border  of  the  sterno- 
cleidomastoid muscle,  and  retract  this  nuisde  laterally  outward.  Do 
not  disturb  the  relationship  of  these  parts  by  dissection.  Identify  the 
carotid  artery  and  the  large  vagus  nerve  right  neighboring.  In  addi- 
tion, identify  two  delicate  nerves,  one  white  and  one  gray  in  color. 
The  former  are  the  depressor  fi])ers  of  the  vagus  which  pursue  a  separate 
course  in  the  rabbit,  and  the  latter,  the  sympathetic  fibers  uniting  the 
inferior  and  superior  cervical  ganglia  of  this  sys- 
tem. Place  each  in  a  loose  silk  ligature.  Shift 
the  head  of  the  animal  so  that  the  ear  on  the 
side  operated  on  may  be  placed  in  a  position  for 
inspection.  Hold  an  incandescent  lamp  behind 
it.  Identify  the  central  artery  of  the  ear  and 
the  lateral  venous  collecting  channels.  Arrange 
the  electric  apparatus  for  stimulation  with  a 
quickly  interrupted  current  of  very  moderate 
intensity.  Gently  raise  the  cervical  sj'mpath- 
etic  nerve  from  the  wound  and  place  it  in 
small  shielded  electrodes.  Stimulate  for  a 
period  of  about  fifteen  to  twenty  seconds.    Note  Fig.  75.— Shielded 

that  after  an  appreciable   latent   period  the       iHarvfrfApmrafus  Co.) 
central  artery  becomes    less    conspicuous  and 

eventually  disappears  altogether.  Discontinue  the  stimulation  and 
allow  circulatory  conditions  to  become  normal  again.  What  conclusions 
may  be  drawn  from  this  experiment  regarding  the  vasomotor  action  of 
this  nerve? 

Raise  the  cervical  sympathetic  nerve  and  cut  it  between  two  liga- 
tures. Inspect  the  blood-vessels  of  this  ear.  Note  that  its  vascularity 
is  now  much  greater  than  before  and  exceeds  that  of  the  opposite  organ. 
It  also  possesses  a  higher  temperature.  Obviously,  the  division  of  this 
nerve  has  given  rise  to  a  relaxation  of  the  blood-vessels  of  the  correspond- 
ing ear.  Stimulate  the  distal  end  of  the  divided  nerve  and  repeat  the 
observations  made  previously  (Fig.  76). 

It  might  be  well  to  allude  at  this  time  to  the  influence  of  this  nerve 
upon  the  size  of  the  pupil,  although  the  student  cannot  be  expected  as 
yet  to  be  famihar  with  this  particular  reaction.     Since  the  cervical 

117 


118 


ADVANCED    LESSONS   IN    PRACTICAL    PHYSIOLOGY 


sympathetic  nerve  contains  certain  fibers  which  innervate  the  radial 
muscle  cells  of  the  iris,  its  excitation  must  give  rise  to  an  increase  in  the 
size  of  the  pupil.  Consequently,  if  any  doubt  exists  as  to  the  character 
of  the  nerve  isolated,  this  reaction  may  be  employed  to  make  sure  that 
it  is  the  sympathetic. 


Fig.  76. — The  Vasomotor  Reaction  in  the  Ear  of  the  Rabbit  on  Division  and 

Stimulation  of  the  Cervical  Sympathetic  Nerve. 

A,  Normal.    B,  After  division  of  the  cervical  sympathetic  nerve.    C,  On  stimulation  of  the 

distal  end  of  the  divided  cervical  sympathetic  nerve. 

2.  The  Depressor  Nerve. — Insert  a  straight  cannula  in  the  left 
common  carotid  artery  and  connect  it  with  the  mercury  manometer. 
Place  the  depressor  nerve  in  shielded  electrodes,  and  arrange  the  electric 
apparatus  for  stimulation  with  a  quicklj^  interrupted  current  of  mod- 


FiG.  77. — Record  of  the  Carotid  Blood-pressure  in  Rabbit  Durinc;  Stimulation 
OF  the  Depressor  Nerve. 

erate  strength.  Record  the  blood-pressure  and  stimulate  the  aforesaid 
nerve  for  about  twenty  seconds.  Note  the  fall  in  blood-pressure  and 
also  the  decrease  in  the  frequency  of  the  heart.  Allow  the  pressure  to 
return  to  normal. 


THE    CIRCULATION 


119 


Apply  two  lijjatures  to  this  nerve,  a  few  millimeters  apart,  and  cut 
between  them.  Record  the  blood-pressure  and  stimulate  its  central 
and  distal  (heart)  ends  successively  at  intervals.  Since  the  excitation 
of  the  distal  end  remains  inelTective,  what  conclusions  may  be  drawn 
regardinji;  the  direction  of  conduction  in  this  nerve?  What  two  factors 
should  be  held  responsible  for  the  fall  in  blood-pressure? 

Divide  both  vagi  nerves  and  repeat  the  stimulation  of  the  central 
end  of  the  depressor  as  soon  as  the  changes  ordinarily  following  the 
section  of  the  aforesaid  nerves,  have  })ec<)me  thoroughly  established. 
Observe  that  hencefoith  the  fall  in  blood-pressure  is  no  longer  asso- 
ciated with  a  reduction  in  the  frequency  of  the  heart.  Give  a  detailed 
explanation  of  the  function  of  the  depressor  nerve,  and  mention  condi- 
tions liming  which  this  mechanism  is  called  into  plaj\ 

t 


SL 


Fig.  7S. — DiAr,R.\M  to  Show  the  Covrse  of  the  Depressor  Nerve  in  the  Rabbit. 
L,  Larj'nx;  T,  thyroid  gland;  j,  int.  jugular  vein;  C,  carotid  artery;  S,  sympathetic 
nerve  extending  between  the  superior  and  inferior  cervical  ganglia;  V,  vagus  nerve; 
iSL,  sup.  lar\-ngeal  nerve;  D,  depressor  nerve,  entering  the  vagus  by  two  branches. 
The  vagus  is  pulled  over,  permitting  the  sj-mpathetic  to  appear  next  to  the  carotid  artery. 

3.  The  Sciatic  Nerve. — Test  the  artificial  respiration  apparatus  and 
connect  the  ether-bottle  with  the  tracheal  cannula.  Prepare  a  solution 
of  curare.  Inject  1  c.c.  of  this  solution  intravenously  bj'  means  of  a 
syringe.  Allow  this  agent  to  produce  its  characteristic  effect,  and 
institute  artificial  respiration  as  soon  as  the  diaphragm  shows  the  first 
indications  of  ceasing  its  action  (fifteen  minutes).  Expose  the  sciatic 
nerve  in  the  thigh;  place  a  ligature  upon  it,  and  cut  it  distally  to  the 
ligature.  Record  the  carotid  pressure  and  stimulate  the  central  end 
of  this  nerve  with  a  quickly  interrupted  current  of  moderate  strength. 
As  a  rule,  currents  of  medium  strength  and  frequency  give  rise  to  a 
reflex  vasoconstriction,  and  hence  to  an  increase  in  the  carotid  blood- 
pressure.  Since  the  motor  plates  of  the  skeletal  musculature  have  been 
paralyzed  by  the  curare,  this  result  cannot  be  referred  to  the  mechanical 
influence  of  contracting  muscle  tissue. 


120         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

Weaken  the  strength  of  the  current  considerably  by  moving  the 
secondary  coil  farther  away  from  the  primary.  Stimulate  the  nerve  in 
the  same  manner  with  single  induction  shocks  repeated  at  intervals  of 
about  half  a  second.  This  procedure  usually  gives  rise  to  a  reflex  vaso- 
dilatation, and  hence  to  a  fall  in  the  carotid  blood-pressure.  Conse- 
quently, the  sciatic  nerve  contains  vasoconstrictor  as  well  as  vaso- 
dilator fibers.     Kill  the  animal  by  an  overdose  of  ether. 

Annotation. — In  isolating  the  sciatic  nerve  make  use  of  the  following  landmarks: 
Seek  a  point  midway  between  the  ischium  and  great  trochanter  of  the  femur,  and 
draw  an  imaginary  Hne  from  here  to  the  anterior  aspect  of  the  knee-joint.  Direct 
the  incision  along  this  line  about  the  middle  of  the  thigh  and  separate  the  adjoining 
muscles  until  the  fatty  tissue  investing  the  sciatic  nerve  has  been  exposed. 


LESSON  XXIII 
THE  CIRCULATION  (Continued 

THE   VASOMOTOR    ACTION    OF    THE   GREATER    SPLANCHNIC   NERVE. 
THE  VASCULARITY  OF  THE  KIDNEY.     ONCOMETRY 

I.  The  Greater  Splanchnic  Nerve.  Aiicstlictizt'  a  cat  and  maintain 
deep  anestlit\^ia  thioiijiliout  tlic  followinfi  exporinicnts:  Perform  trache- 
otomy. Insert  a  straight  eanimla  in  the  left  common  carotid  artery 
and  arrange  the  apparatus  for  recording  the  blood-pressure.  jVIake  a 
median  incision  through  the  skin  of  the  abdomen  and  incise  the  Unea 
alba.  Introduce  the  middle  and  index-fingeis  (jf  your  left  hand  through 
this  opening  and  l)y  using  them  as  a  guitle  enlarge  the  incisitjn  upward 
as  far  as  the  ensiform  cartilage,  and  downward  as  far  as  the  region  of 


Fig.  79. — Region  of  Left  Kidney. 
JC,  Inferior  vena  rava;  RV,  renal  vein;  K,  kidney;  SC.  left  adrenal  body  with  cor- 
responding vein;  S,  greater  splanchnic  nerve;  .-l,  abdominal  sympathetic  nerve:  M,  minor 
splanchnic    nerves,  from  luml)ar  ganglia  to  suprarenal    plexus  below  adrenal   body;  D, 
diaphragm;  TS,  thoracic  sympathetic  ner^e. 

the  bladder.     Apply  a  cloth  moistened  with  warmed  saline  solution  to 
the  abdomen. 

Arrange  the  electric  apparatus  for  stimulation  with  a  quickly  inter- 
rupted current  of  medium  strength.  Procure  a  pair  of  small  shielded 
electrodes  and  connect  them  with  the  secondary  coil  of  the  inductorium. 
Ask  the  assistant  to  expose  the  region  above  the  left  kidney,  holding 
this  organ  and  the  liver  away  from  the  field  of  operation.  Identify  the 
left  .■suprarenal  body  at  the  junction  of  the  left  suprarenal  vein  with  the 
inferior  vena  cava.  It  appears  as  a  rounded,  pea-shaped  mass,  possess- 
ing a  pink  color.     With  two  forceps  spUt  the  peritoneum  and  fascia 

121 


122 


ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 


along  its  right  (as  you  look  at  it)  upper  margin.  Very  carefully  search 
for  a  small  nerve  in  the  fatty  tissue  of  this  region  pursuing  an  oblique 
course  upward  through  the  crus  of  the  diaphragm.  This  is  the  left 
greater  splanchnic  nerve,  connecting  the  thoracic  sympathetic  system 
with  the  solar  plexus.  Place  a  loose  silk  ligature  around  it  and  secure 
it  in  shielded  electrodes.  Insulate  by  means  of  a  narrow  piece  of  rubber 
membrane  and  dry  cotton.  Allow  the  parts  to  close  in  around  the 
electrodes  and  apply  a  warm  cloth  to  the  abdomen. 

Allow  the  carotid  blood-pressure  to  be  recorded.     Stimulate  the 
aforesaid  nerve  for  about  ten  seconds  until  j^ou  have  obtained  an  appre- 


FiG.  so. — Splanchnic  Rise  in  Blood-pressure. 


ciable  rise  in  pressure, 
the  clip  to  the  artery. 


Repeat  this  procedure  after  an  interval.    Apply 
Study  the  character  of  the  tracing  so  obtained. 


Annotation. — The  rise  in  blood-pressure  usually  consists  of  two  phases.  The 
first  is  brought  about  by  the  vasoconstriction,  resulting  in  the  so-called  splanchnic 
organs  in  consequence  of  the  excitation  of  this  nerve.  This  rise  appears  within  a 
few  seconds  after  the  onset  of  the  stimulation  and  finds  its  origin  in  a  rapid  transfer 
of  blood  from  the  abdominal  organs  into  the  channels  of  the  general  circulatory 
system.  The  second  rise  ai)pears  about  ten  seconds  after  the  first,  and  is  due  to  the 
constriction  of  the  blood-vessels  of  the  general  system  by  the  adrenin  liberated  in 
consequence  of  the  excitation  of  this  nerve.  Obviously,  only  the  left  adrenal  body  is 
involved,  because  the  innervation  of  these  organs  by  the  splanchnic  nerve  is  uni- 
lateral. 

Iiccord  the  blood-pressure.  Quickly  tighten  the  silk  ligature  so  as 
to  crush  this  nerve.     Observe  the  gradual  fall  in  pressure  which  is 


THE    ClUcrLATION  123 

brought  about  by  the  fact  that  the  aluloiiiinal  blood-vessels  innervated 
by  this  nerve,  lose  their  tonus  and  relax.  Consequently,  a  certain 
quantity  of  i)l()od  will  now  find  its  way  from  the  K^meral  circulation 
into  the  relaxed  blood-vessels  of  the  splanchnic  organs. 

Apply  the  shielded  electrodes  to  the  distal  (abdominal)  end  of  the 
divided  nerve.  Replace  the  ai)dominal  organs  and  cover  the  abdomen 
with  a  warm,  moist  cloth.  Record  the  blood-pressure  and  stimulate 
the  splanchnic  nerve  as  described  above.  Owing  to  the  lower  general 
pressure,  the  rise  will  now  be  more  pronounced.  Disconnect  the  man- 
ometer andHgate  the  carotid  artery. 

2.  The  Vasomotor  Supply  of  the  Kidney. — Procure  an  oncometer 
large  enough  to  contain  the  kidney  of  this  animal.  Fill  the  outer  com- 
partments of  this  instrument  with  warm  water  until  their  membranous 
inner  walls  have  become  moderately  distended.  Separate  the  left 
kidney  from  the  fatty  tissue  surrounding  it,  but  do  not  injure  its  cap- 
sule. Place  the  lower  hemispheric  part  of  the  oncometer  underneath 
this  organ.  Adjust  its  cover  so  that  the  kidney  assumes  a  central 
position  between  the  rubber  membranes,  taking  special  care  that  its 
blood-vessels  as  well  as  the  ureter  pursue  a  perfectly  normal  course 
through  the  slit-like  lateral  orifice  of  the  oncometer.  Connect  the 
compartment  in  the  cover  of  this  instrument  by  means  of  a  piece  of 
rubber  tul)ing  with  a  membrane  tambour  or  piston  recorder.  It  is  not 
essential  that  this  connecting  tube  be  filled  with  water.  Cover  the 
abdomen  with  a  warm,  moist  cloth. 

Register  the  excursions  of  the  recording  lever  upon  the  smoked 
paper  of  a  slowly  revolving  kymograph.  Observe  that  the  volume  of 
the  kidney  undergoes  cardiac  and  respiratory  variations,  i.  e.,  it  is 
increased  during  each  systoHc  phase  of  the  heart  and  suffers  a  more 
general  increase  during  the  entire  inspiratory  period. 

Temporarily  obstruct  both  femoral  arteries.  Note  the  effect  upon 
the  volume  of  the  kidney.  Explain.  Temporarily  occlude  the  carotid 
arteries.     Observe  the  change  in  the  volume  of  the  kidney.     Explain. 

Adjust  the  shielded  electrodes  to  the  distal  end  of  the  divided  left 
greater  splanchnic  nerve.  While  registering  the  volume  curve  of  the 
corresponding  kidney  stimulate  this  nerve  with  a  quickly  interrupted 
current  of  moderate  strength.  Account  for  the  decided  reduction  in 
its  volume.     Kill  the  animal  by  an  excessive  amount  of  ether. 

Dissect  the  region  of  the  left  kidney  and  adrenal  body.  Identify 
the  organs  on  the  opposite  side,  and  also  the  suprarenal,  mesenteric,  and 
celiac  ganglia  and  plexuses  of  the  solar  sympathetic  system.  Trace 
the  greater  splanchnic  nerve  into  the  thorax,  identifj'ing  the  thoracic 
sympathetic  nerve  and  stellate  ganglion.  Enucleate  the  adrenal  bodies. 
Bisect  them  and  identify  their  cortical  and  medullary  portions. 

3.  Vasomotor  Phenomena  in  Man.^Fill  a  large  Ijeaker  with  ice- 
water  and  another  with  water  heated  to  40°  C.  Introduce  your  hands 
for  a  short  time.  Withdraw,  and  note  the  effect  upon  the  color  and 
condition  of  the  skin.     Explain. 


LESSON  XXIV 

THE  CIRCULATION  (Continued) 

THE  INDIRECT  METHOD  OF  MEASURING  BLOOD-PRESSURE.     EFFECT 
OF  POSTURE  AND  EXERCISE 

1.  The  Application  of  the  Sphygmomanometer. — Place  the  index- 
finger  of  your  left  hand  upon  the  skin  over  the  brachial  artery  of  the 
subject.  Palpate  the  radial  pulse  with  the  index-  and  middle  fingers 
of  your  right  hand,  (lently  compress  the  brachial  artery  vmtil  the 
radial  pulse  can  no  longer  be  felt. 

Place  the  index-finger  of  your  left  hand  upon  the  skin  over  the 
brachial  artery.     With  your  right  hand  adjust  the  chest-piece  of  a 


Fig.  M.— 1;i\  \-1; 


M'li-i' , Ml  iM  \  \<  i\i KTEU,  Early  Type.     (From  J(niciriiy'.i  "Clinical 
Sludy  (if  Blood-pressure.") 


stethoscope  upon  the  flexor  surface  of  the  elbow-joint.  Do  you  hear  a 
sound?  Gently  compress  the  brachial  artery.  Describe  the  character 
of  the  sound  now  heard.     Explain  its  cause. 

The  sphygmomanometer  most  commonly  used  in  making  these  tests 
consists  of  (a)  a  mercury  manometer,  (6)  a  narrow  rubber  cuff  to  fit 
around  the  arm,  and  {c)  an  inflating  bulb  with  exhaust  valve.  In  the 
sphygmotonometer  the  place  of  the  mercurial  indicator  is  taken  by  a  steel 

125 


126 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


spring  which  must  be  cahbrated  from  time  to  time  by  comparing  its 
movements  with  those  of  a  column  of  mercury  under  equal  degrees  of 
pressure.  Since  the  mercurj^  manometer  usually  consists  of  one  vertical 
hmb  leading  away  from  a  central  reservoir,  the  pressure  may  be  read 
off  directly  without  correction.  Some  instruments,  however,  contain  a 
U-shaped  tube,  in  which  case  the  pressure,  as  read  off  from  the  ascend- 
ing limb,  must  be  multiplied  by  2. 


Fig.  82. — Sphygmomanometer,  Recent  Type.    (Manufactured  by  W.  A.  Baum  Co.,  N.  Y.) 

The  subject  should  be  comfortably  seated  in  a  chair  with  his  right 
forearm  resting  upon  a  table.  Adjust  the  arm  piece  of  the  sphyg- 
momanometer (modification  of  the  Riva-Rocci  instrument)  to  the  arm 
of  the  subject.  Be  sure  that  the  lower  edge  of  the  cuff  does  not  encroach 
upon  the  elbow  and  is  not  applied  too  loosely.  Two  methods  may  be 
followed  in  determining  the  blood-pressure,  namely,  palpation  and 
auscultation. 

(a)  PaljMtion. — Having  adjusted  the  armpiece  accurately,  locate  the 


THE    flUCULATION  127 

radial  pulse  with  (lu>  fiii^ois  of  (ho  lijihl  hand.  T'loso  tho  oxhaust  valve 
and  compress  the  nihher  hull)  rapidly  to  raise  the  pressure  to  ai)out 
140  nun.  Hjj;.  In  a  youiifj;  person  possessint^  an  (>lastie  vascular  system 
and  in  the  sittinf;  position,  we  would  not  expect  to  find  a  pressure  higher 
than  this.  Consequently,  the  pressuie  in  the  cuff  overcomes  at  this 
time  the  internal  picssure.  The  brachial  artery  is  fully  compressed 
and  the  radial  pulse  ohliterated.  Now  gradually  deflate;  until  the  radial 
pulse  just  barely  makes  itself  felt.  Read  the  pressure  and  deflate  rap- 
idly. Be  sure  to  compress  the  arm  for  only  the  shortest  possible  time. 
Repeat  agafii  after  intervals  until  you  have  acquired  this  technic  thor- 
oughly and  are  able  to  obtain  correct  results.  This  gives  the  systolic 
blood-pressure. 

(6)  Auscultation. — Place  the  chest-piece  of  a  stethoscope  over  the 
region  of  the  bifurcation  of  the  brachial  artery  directly  below  the  lower 
edge  of  the  cuff.  Inflate  rapidly  as  before,  then  deflate  gradually.  No 
sound  is  heard  when  the  brachial  artery  is  obstructed.  At  the  very 
moment,  however,  when  the  arterial  pressure  just  overcomes  the  out- 
side pressure  a  sound  is  produced  indicative  of  the  systolic  gushes  of 
blood  through  the  constriction.  Read  the  pressure,  which,  as  has  just 
been  stated,  is  the  systolic.  Practice  this  method  a  number  of  times. 
Compare  these  results  with  those  obtained  previously  by  palpation. 

The  estimation  of  the  diastolic  pressure  may  be  attempted  during 
the  process  of  palpation  by  carefully  noting  the  amplitude  of  the  oscilla- 
tions of  the  mercury  of  the  manometer.  When  the  systolic  pressure 
breaks  through  the  constriction  these  fluctuations  are  small,  but  become 
much  larger  as  the  diastolic  value  is  approached.  Below  this  point 
their  amplitude  again  decreases.  A  better  way  is  to  ascertain  this 
value  by  the  method  of  auscultation.  Having  determined  the  moment 
when  the  systolic  sound  just  appears,  continue  to  deflate  slowly.  The 
sound  becomes  louder;  soon  reaches  a  maximum,  and  then  suddenly 
disappears.  Read  the  pressure  at  this  point.  It  indicates  the  diastoUc 
pressure. 

Deduct  the  value  of  the  diastolic  pressin'o  from  that  of  the  systolic. 
This  gives  the  pulse-pressure,  which  varies  under  ordinary  conditions 
between  35  and  40  nun.  Hg. 

2.  Effect  of  Posture. — Determine  the  systolic  and  diastolic  pressures 
of  the  subject  while  resting  horizontally  upon  the  table  with  his  head 
upon  a  pillow.  Repeat  this  test  after  he  has  assumed  the  sitting  posi- 
tion, and  again  after  he  has  assumed  the  standing  position.  Tabulate 
the  results  and  determine  the  pulse-pressure.  Explain  the  results. 
What  bearing  do  they  possess  upon  the  condition  of  the  vascular  sj'stem? 

Crampton  has  attempted  to  obtain  an  approximate  estimate  of  the 
condition  or  vascular  tone  of  a  person  bj^  balancing  the  increase  in  the 
heart  rate  with  the  increase  or  decrease  in  blood-pressure  resulting  on 
standing  up.  The  range  of  the  sj'stolic  pressure  has  been  found  to  be 
between  -|-10  and  — 10  mm.  Hg,  and  the  increase  in  the  frequency  of 
the  heart  between  0  and  44.     By  assigning  equal  percentages  to  these 


128         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

the  following;  scale  has  .been  constructed,  in  accordance  with  which  the 
vascular  tone  may  be  expressed  in  percentages: 

Heart  rate,  Systolic  blood-pressure, 

increase.  , Increase .       . Decrease . 

+  10     +8     +6     +4     +2  0        -2     -4      -6     -8     -10 

Oto    4 100  95  90  85  80  75  70  65  60  55  50 

5  to    8 95  90  85  80  75  70  65  60  55  50  45 

9  to  12 90  85  80  75  70  65  60  55  50  45  40 

13  to  16 85  80  75  70  65  60  55  50  45  40  35 

17  to  20 80  75  70  65  60  55  50  45  40  35  30 

21  to  24 75  70  65  60  55  50  45  40  35  30  25 

25  to  28 70  65  60  55  50  45  40  35  30  25  20 

29  to  32 65  60  55  50  45  40  35  30  25  20  15 

33  to  36 60  55  50  45  40  35  30  25  20  15  10 

37  to  40 55  50  45  40  35  30  25  20  15  10  5 

41  to  44 50  45  40  35  30  25  20  15  10  5  0 

Thus,  a  person  who  on  standing  up  shows  an  increase  in  the  cardiac 
rate  of  10  beats,  and  an  increase  in  the  blood-pressure  of  10  mm.  Hg, 
would  be  in  the  condition  A  (95  per  cent.). 

Barach  calculates  the  energy-index  in  accordance  with  the  following 
example : 

Pressure.  Heart  rate.  Index. 

In  systole 120  mm.  Hg       X      72      =        8.640  mm.  Hg 

In  diastole 70  mm.  Hg       x      72      =        5.040  mm.  Hg 

In  both 190  mm.  Hg       X      72      =       13.680  mm.  Hg 

The  highest  energy-index  in  a  still  normal  person  has  been  found  to 
lie  close  to  20,000  mm.  Hg  in  a  minute,  and  the  lowest  somewhere 
about  10,000. 

3.  The  Effect  of  Exercise. — Determine  the  normal  systolic  blood- 
pressure  and  rate  of  the  heart  with  the  subject  standing.  Repeat  these 
determinations  immediately  after  the  subject  has  made  forty  flexions 
and  extensions  of  the  arms  or  thirtj^  knee  bendings  in  one  minute.  Re- 
peat one,  two,  three,  four,  and  five  minutes  afterward.  Construct  a 
curve  to  show  the  course  of  the  pressure  and  cardiac  frequency. 

Determine  the  cardiac  frequency  and  blood-pressure  in  a  subject 
before  and  after  he  has  made  a  stationary  run  lasting  one-half  minute. 

Determine  the  cardiac  frequency  and  blood-pressure  in  a  subject 
before  and  after  he  has  ascended  forty  steps  in  the  course  of  one  minute. 

4.  Venous  Pressure. — Hold  the  hand  against  thfe  chest  in  the  region 
of  the  heart.  Note  the  degree  of  filling  of  the  veins.  Raise  the  hand 
slowly  until  the  veins  collapse.  Determine  the  distance  between  this 
level  and  the  level  of  the  heart.  It  corresponds  to  the  height  of  the 
column  of  blood  supported  by  the  heart. 


LESSON  XXV 

THE  CIRCULATION  (Concluded) 

THE    CHARACTER    AND    VELOCITY    OF    THE    ARTERIAL    AND    VENOUS 
PULSATIONS.     POLYGRAPHY 

1.  The  Application  of  the  Sphygmograph. — Determine  the  rate  of 
the  subject's  licart  l)y  palpation  of  the  radial  pulse.  How  is  the  rate 
affected  by  the  act  of  swallowinsi;? 

Study  the  construction  of  the  sphyj2;mo^raph.  It  usually  consists 
of  a  vibrating  rod  which  acts  in  magnified  form  upon  a  recording  lever. 
The  end  of  the  rod  is  equipped  with  an  oval  projection  which  is  adjusted 
over  the  artery.  Apply  this  instrument  securely  to  the  radial  artery 
and  record  a  number  of  normal  sphygmographic  curves.  Study  their 
character. 


Fig.  83. — The  Dudgeon  Sphygmograph  in  Position.     (Howell.) 

Ask  the  subject  to  close  his  mouth  and  nostrils  with  the  fingers  of 
the  free  hand  and  exhale  forcibly.  Explain  the  result  (Valsalva's 
experiment) . 

2.  Relation  Between  the  Arterial  Pulse  and  the  Action  of  the  Heart. 
— Obtain  a  sphygmographic  record  of  the  radial  pulse  in  proper  relation 
with  a  record  of  the  apex-beat  registered  by  means  of  a  cardiograph. 
Note  whether  any  extrasystoles  are  present. 

Allow  a  cardiograph  and  a  sphygmograph  (radial  artery)  to  register 
their  excursions  in  the  same  ordinate  upon  a  rapidly  rotating  drum, 
above  the  record  of  a  tuning-fork.  Obtain  the  approximate  distance 
between  the  ascending  aorta  and  the  radial  artery,  and  ascertam  the 
speed  of  the  pulse- wave  by  comi:)uting  the  difference  of  the  cardiac  and 
radial  impulses. 

3.  The  Use  of  the  Phlebograph. — Apply  a  metal  or  glass  cup  to 
the  jugular  fossa  and  connect  it  with  a  recording  tambour.     Also  register 

9  129 


130         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

the  time.  Study  the  character  of  the  phlebogram,  and  compare  it  with 
the  curve  of  intra-auricular  pressure.  Under  what  conditions  does  the 
phlebogram  become  of  special  value?  What  changes  would  tricuspid 
regurgitation  produce  in  the  character  of  the  tracing? 

Obtain  a  phlebogram  in  proper  relation  with  a  sphygmogram  of  the 
radial  artery,  or  with  a  cardiogram.  When  would  a  record  of  this  kind 
prove  of  special  diagnostic  value? 


L 


Fig.  84. — Pneumograph.     (Harvard  Apparatus  Co.) 

Annotation. — As  the  name  indicates,  a  jugular  cup  consists  of  a  hemispheric 
capsule  of  metal  or  glass  which  is  placed  flat  against  the  region  of  the  central  end  of 
the  external  jugular  vein.  The  pulsations  of  tlais  blood-vessel  are  transmitted  to 
a  recording  drum. 

4.  Relation  Between  the  Cardiac  and  Respiratory  Activities. — Ad- 
just a  stethograph  upon  the  chest  of  the  subject  and  connect  it  with  a 
recording  tambour.  Place  a  receiving  cup  over  the  region  of  the  carotid 
artery  and  connect  it  with  a  recording  drum  arranged  to  register  in  the 


Fig.  85. — Marey's  Pneumograph.  (Verdin.) 
The  instrument  consists  of  a  tambour  (0,  mounted  on  a  flexible  metal  plate  (p).  By- 
means  of  the  bands  c  and  c  the  metal  plate  is  tied  to  the  chest.  Any  increase  or  decrease 
in  the  size  of  the  chest  will  then  affect  the  tambour  by  the  lever  arrangement  shown  in 
the  figure.  These  changes  in  the  tambour  are  transmitted  through  the  tube  r  as  pressure 
changes  in  the  contained  air  to  a  second  tambour  (not  shown  in  the  figure)  which  records 
them  upon  a  smoked  drum.     (Howell.) 

same  vertical  line  as  the  former.  Beneath  these  writing  levers  adjust 
the  marker  of  a  Jaquet  chronograph.  While  the  subject  assumes  a 
perfectly  inattentive  attitude,  record  a  number  of  respiratory  cycles 
upon  a  drum  revolving  at  a  moderate  speed.  How  many  cardiac  cycles 
does  each  respiratory  cycle  embrace?  Do  you  observe  an  increase  in 
the  cardiac  frequency  on  inspiration?     Explain  this  variation. 

Annotation. — A  simple  stethograph  may  be  made  by  fastening  a  small  rubber 
pouch  by  means  of  a  broad  linen  strap  against  the  chest.  The  single  orifice  of  this 
pouch  is  connected  Vjy  means  of  a  cannula  and  a  piece  of  rubber  tubing  with  a  record- 


THE    CIUCULATION  131 

ing  tamhour.  Anotlier  convenient  form  consists  of  a  long  rubber  tube  about  2 
cm.  in  diameter  and  closed  at  one  end.  Its  otlu-r  end  is  connected  with  a  recording 
tambour  by  means  of  small  tubing  (Fig.  S 4).  The  interior  of  the  hirge  tube  is  occii- 
l)ied  by  a  long  spiral  spring.  When  applied  transversely  around  the  chest  this  tube 
will  be  lengthened  on  inspiration  and  air  will  be  drawn  into  it,  c-ausing  the  membrane 
of  the  recording  tambour  to  be  displaced  inward.  On  expiration,  the  recoil  of  the 
tube,  aided  by  the  spiral,  increases  the  pressure  within  its  lumen  and  forces  the 
rubber  membrane  of  the  tambour  outward.  Marey's  stethograph  (Fig.  So)  consists 
of  a  metal  plate  which  is  fastened  to  the  surface  of  the  chest  by  means  of  a  strap. 
The  changes  in  the  tension  of  this  plate  suffered  by  it  in  con.sequence  of  the  respira- 
tory movements,  are  conunimicated  by  means  of  a  lever  to  a  receiving  drum.  The 
latter,  in  turn,  communicates  with  a  recording  drum. 


LESSON  XXVI 

RESPIRATION 

MECHANICS  OF  RESPIRATION 

1.  The  Spirometer. — Study  the  construction  of  the  spirometer 
(Hutchinson).  Breathe  normally,  then  close  the  nostrils  and  exhale 
normally  through  the  mouthpiece  of  this  instrument.  Determine  the 
movement  of  the  pointer  and  calculate  the  volume  of  the  tidal  air. 


Fig.  86. — Winthich's  Modification  of  Hutchixsox's  Spirometer.     (Reichert.) 

Breathe  normally;  then  exhale  forcibly  through  the  mouthpiece. 
Determine  the  volume  of  the  supplemental  air. 

Set  the  spirometer  at  5000  c.c.  Breathe  normally ;  then  inspire  deeply 
through  the  mouthpiece.  Determine  the  volume  of  the  complemental 
air, 

133 


134 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


Set  the  spirometer  at  zero.  After  several  normal  respirations,  in- 
spire as  deeply  as  possible  and  immediately  expire  as  much  as  possible 
through  the  mouthpiece  of  the  spirometer.     Ascertain  the  vital  capacity. 

2.  Schema  Illustrating  the  Action  of  the  Thorax.— Examine  the  con- 
struction of  the  model  represented  in  Fig,  87. 

(a)  Normal  Respiration. — Lower  and  raise  the  rubber  membrane 
closing  the  bell-jar.  Observe  that  the  rubber  pouch  representing  the 
lung  is  expanded  during  the  first  movement,  and  decreased  in  size 
during  the  second.  Clearly,  these  changes  are  brought  about  by  an 
action  upon  the  entire  external  surface  of  the  rubber  pouch.  When  the 
pressure  in  the  "intrapleural  space"  (between  the  surface  of  the  rubber 
pouch  and  the  wall  of  the  bell-jar)  is  decreased  by  the  downward  move- 


FiG.  87. — Apparatus  Illustrating  the  Expansion  of  the  Lung,     (Laulanie.) 
n.  Bell  jar;  B,  lung  in  form  of  rubber  balloon;   M,  manometer  in  connection  with 
"intrapleural  space."     Another  manometer  may  be  connected  with  the  inlet-tube  to 
register  the  "intrapulmonic  pressure." 

ment  of  the  "diaphragm"  (rubber  membrane),  the  walls  of  the  "lung" 
(rubber  pouch)  are  pulled  uniformly  outward.  An  area  of  low  pressure 
is  thereby  established  within  the  "lungs,"  forcing  a  certain  quantity  of 
air  to  flow  through  the  "trachea"  (inlet  tube)  into  the  pouch.  The 
reverse  relationships  are  established  by  the  upward  movement  of  the 
"diaphragm,"  simulating  expiration. 

The  two  manometers  fastened  to  the  top  of  this  model  are  connected, 
on  the  one  hand,  with  the  "intrapleural  space"  and,  on  the  other,  with 
the  "trachea,"  Carefully  observe  the  variations  in  the  pressures  dur- 
ing inspiration  and  expiration,  showing  that  the  fall  in  "intrapleural 
pressure"  is  responsible  for  the  expansion  of  the  "lung"  and  the  subse- 
quent influx  of  air  into  its  spaces.     Normally,  of  course,  the  intrapleural 


RESPIRATION  135 

space  is  a  capillary  space  filled  with  pleural  fluid.  This  implies  that  the 
surface  of  the  lung  is  everywhere  in  dose  coiita(!t  with  the  inner  surface 
of  the  wall  of  the  thorax. 

(b)  Forced  Respiration.-  IjOwvv  and  raise  the  "diaphragm"  more 
forcibly,  thereby  producing  a  more  ample  expansion  of  tlie  ''lung"  and 
more  decisive  variations  in  pressure. 

(c)  Dyspnea  and  Asphyxia.^Tho  former  condition  may  be  repro- 
duced in  a  mechanical  way  l)y  partially  closing  the  stop-cock  with  which 
the  inlet  tul)(>  is  equipped.  This  would  coirc'spond  to  an  incomplete 
closure  of  the  trachea  and  would  greatly  imj)air  the  interchange  of  the 
respiratory  air.  Note  the  resistance  now  acting  against  the  "dia- 
phragm." Obviously,  this  diminution  in  the  caliber  of  the  inlet  tube 
must  augment  the  variations  in  the  intrapleural  and  intrapulmonic 
pressures. 

Close  the  stop-cock  completely,  simulating  the  condition  of  asphyxia, 
or  complete  absence  of  air. 

(d)  Collapse  of  the  Lungs. — Expand  the  "lung"  by  moving  the 
"diaphragm"  downward.  Suddenly  permit  air  to  rush  into  the  "intra- 
pleural" space  by  slightly  tilting  the  rubber  cork  closing  the  upper 
orifice  of  the  bell-jar.  Observe  the  immediate  loss  of  "intrapleural" 
pressure  and  collapse  of  the  "lung."  Having  in  this  way  destroyed  the 
"intrapleural"  pressure,  endeavor  to  expand  the  "lung"  by  moving  the 
"diaphragm"  downward. 

3.  Application  of  Above  Principles  to  the  Thorax  of  the  Mammal. — 
Anesthetize  a  cat  and  maintain  the  anesthesia  throughout  the  following 
experiments:  Perform  tracheotomy.  Make  a  median  incision  through 
the  skin  in  the  midventral  line  of  the  body,  beginning  near  the  tip  of 
the  sternum  and  extending  well  along  the  linea  alba.  Reflect  the 
skin  on  each  side  so  as  to  expose  the  ventral  aspect  of  the  thorax.  Study 
the  mechanism  of  normal  respiration.  Note  the  excursions  of  the 
diaphragm  and  contraction  of  the  neighboring  intercostal  muscles. 
Observe  the  downward  movement  of  the  liver  and  stoniach  on  inspira- 
tion. Which  part  of  the  chest  is  affected  most  in  quiet  breathing? 
Produce  forced  respiration  by  partially  closing  the  rubber  tube  attached 
to  the  tracheal  cannula.  The  normally  diaphragmatic  type  of  respira- 
tion is  now  gradually  augmented  by  costal  respiration.  Observe  also 
that  the  accessory  movements  of  respiration  are  now  much  more  con- 
spicuous. 

4.  Action  of  the  Diaphragm. — Open  the  abdominal  cavity  by  an 
incision  through  the  linea  alba.  Petract  the  margins  of  the  wound  and 
depress  the  liver.  Observe:  (a)  The  nmscular  and  tendinous  portions 
of  the  diaphragm,  (6)  the  general  shape  of  this  septum,  (c)  the  course 
of  the  fibers  composing  its  muscular  part,  (d)  the  manner  of  attachment 
and  insertion  of  these  fibers,  and  (e)  the  character  of  their  contraction. 

Determine  the  distance  traversed  by  the  tendinous  portion  of  the 
diaphragm  on  quiet  inspiration.  Identify  the  complemental  space, 
bounded  by  the  upper  surface  of  the  diaphragm  and  the  opposite  wall 


13G         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

of  the  chest.  Observe  that  this  space  is  widened  on  inspiration  and 
that  the  lower  borders  of  the  lungs  are  then  drawn  into  it.  Trans- 
illuminate  this  region,  so  that  indi\'idual  alveoli  may  be  made  out.  Note 
that  the  tissue  of  the  lung  is  in  absolute  contact  with  the  tendinous 
portion  of  the  diaphragm. 

5.  Intrapleural  Pressure. — Procure  a  water  manometer.  Color  the 
water  with  a  little  indigo-carmin.  Connect  the  central  tube  of  this 
manometer  with  a  metal  cannula,  about  10  cm.  in  length  and  curved 
at  its  end.  Force  the  end  of  this  cannula  through  the  soft  tissues  of 
the  seventh  intercostal  space  and  immediate^  turn  it  so  that  it  comes 
to  lie  flat  between  the  surface  of  the  lung  and  the  chest  wall.  Do  not 
move  it  excessively,  because  this  might  give  rise  to  a  leakage  of  air 
into  the  intrapleural  space  and  a  collapse  of  the  lung. 

Observe  that  the  hquid  in  the  manometer  is  drawn  toward  the 
chest  as  soon  as  the  end  of  the  cannula  has  perforated  the  wall  of  the 
thorax  and  has  forced  the  lung  tissue  away  from  the  inner  surface  of  the 
chest  wall.  The  .end  of  the  cannula  thus  comes  to  He  between  the 
visceral  and  parietal  layers  of  the  pleura.  The  air  in  this  artificial 
cavity,  and  hence  also  the  liquid  in  the  manometer,  is  exposed  to  the 
elastic  recoil  of  the  lung  tissue.  The  force  of  this  recoil  is  indicated  by 
the  inward  movement  of  the  liquid  (cm.  H2O).  Inasmuch  as  the  lung 
tissue  is  more  highly  stretched  during  the  inspiratory  period,  this  press- 
ure must  fluctuate.  It  approaches  zero  (line  of  atmospheric  pressure, 
760  mm.  Hg)  at  the  end  of  expiration  and  assumes  a  value  of  as  much 
as  — 5  mm.  Hg  (756  to  755  mm.  Hg)  on  quiet  inspiration. 

Partially  occlude  the  rubber  tube  attached  to  the  tracheal  cannula. 
As  the  breathing  assumes  a  labored  character,  these  differences  in  the 
intrapleural  pressure  become  more  apparent  ( — 8  to  — 10  mm.  Hg,  in 
cats) ,  because  the  lung  tissue  is  now  put  under  a  greater  elastic  tension 
than  during  normal  respiration. 

6.  Collapse  of  the  Lung. — Inspect  the  tendinous  portion  of  the  dia- 
phragm through  the  wound  in  the  abdominal  wall.  Note  that  the  pink 
pulmonary  tissue  hes  in  absolute  contact  with  it.  Twist  the  cannula 
slighth',  allowing  air  to  enter  the  pleural  sac.  The  lung  tissue  will  then 
be  seen  to  recoil  from  the  diaphragm  (pneumothorax).  This  procedure 
most  generally  leads  to  the  collapse  of  only  one  lung,  while  the  other 
lung  remains  expansible  and  is  capable  of  effecting  an  adequate  inter- 
change of  the  gases.  Discuss  the  effect  of  placing  the  chest  and  posterior 
part  of  the  animal  in  a  compartment  in  which  a  negative  pressure  may 
be  produced  equaling  the  intrapleural. 

Open  the  cavity  of  the  thorax  by  a  cut  through  the  median  line  of 
the  sternum.  Institute  artificial  respiration  through  the  ether  bottle. 
Note  the  position  of  the  cannula  in  the  now  actual  and  greatly  enlarged 
intrapleural  space.     Withdraw  it. 

Temporarily  discontinue  tlie  artificial  respiration.  Observe  that  the 
respiratory  muscles  continue  to  contract  in  spite  of  the  fact  that  the 
lungs  can  no  longer  be  expanded.     As  the  CO2  accumulates  in  the 


RESPIRATION  137 

system,  stiinulatinji  the  respiratory  center  to  inoreased  activity,  these 
reflex  movements  frequently  assume  a  spasmodic  character. 

Inspect  the  internal  aspect  of  the  chest  wall,  and  note  the  shape 
of  tlie  thoracic  cavity.  Identify  the  pulmonary  Ijlood-vessels.  Trans- 
illuminate  the  border  of  either  lung,  notinfi  its  alveolar  structure.  Iden- 
tify portions  of  the  visceral  pleura  below  the  apex  of  tlie  heart.  Note 
its  structural  peculiarities. 

7.  The  Phrenic  Nerves. — Isolate  both  phrenic  nerves  above  the 
diaphraurm  and  place  tiiem  in  loose  ligatures.  These  nerves  are  easily 
found,  because  they  descend  in  close  proximity  to  the  heart,  the  right 
selecting  the  highway  of  the  inferior  vena  cava.  Stimulate  them 
separately  with  single  induction  shocks  of  moderate  strength.  Observe 
the  resultant  contraction  of  the  corresponding  half  of  the  diaphragm 
and  note  the  effect  of  this  contraction  upon  the  position  of  the  ab- 
dominal organs.     Kill  the  animal  by  an  overdose  of  ether. 

Trace  the  course  of  each  phrenic  nerve  to  its  origin  ui  the  cervical 
portion  of  the  spinal  cord. 

8.  Swim  Test. — Grasp  the  tracheal  cannula  with  your  left  hand, 
and  separate  the  trachea  and  lungs,  together  with  the  heart  and  large 
blood-vessels,  from  the  neighboring  parts.  Place  this  mass  in  water, 
observing  that  the  buoyancy  of  the  lungs  is  sufficient  to  carry  con- 
sideral^le  additional  weight.  How  would  an  atelectatic  lung  behave 
under  these  circumstnnces?  What  use  is  made  of  these  facts  medico- 
legally? 

9.  The  Excised  Lung. — Remove  the  metal  caimula  from  the  model, 
illustrating  the  manner  in  which  the  lungs  are  expanded.  Insert  this 
cannula  in  the  trachea  of  the  excised  lungs,  and  suspend  this  preparation 
in  the  bell-jar.  Repeat  the  observations  made  previously  with  the 
rubber  pouch. 

Remove  the  lungs.  Compress  them  in  the  palm  of  your  hand. 
Are  you  able  thereby  to  expel  all  the  air  from  them?  Repeat  the  swim 
test.     Explain  your  inabiUty  to  render  them  air  free. 


LESSON  XXVII 

RESPIRATION  (Continued) 

STETHOGRAPPiY.   METHODS  OF  ARTIFICIAL  RESPIRATION.    PULMOTOR. 

1.  Frequency  of  Respiration. — Stiuly  the  movements  of  the  thorax 
and  abdomen.  Differentiate  between  diaphragmatic  and  costal  breath- 
iiifj;.  INIeasure  the  cireumferenee  of  the  chest  at  the  level  of  the  nipples 
on  deep  expiration  and  inspiration.  Count  the  number  of  respirations 
of  the  subject  first  in  the  horizontal  and  then  in  the  erect  position. 
Count  again  after  a  stationary  run  lasting  thirty  seconds,  and  again 
after  forty  to  fifty  flexions  and  extensions  of  the  arms  or  knee  bendings. 
Explain  the  result. 

2.  Percussion  and  Auscultation. — Familiarize  yourself  with  the  nor- 
mal percussion  sound  of  the  lungs  as  ol)tained,  say,  in  the  region  below 
the  clavicle.  Outline  the  upper  boundary  of  the  liver  and  the  area 
of  cardiac  dulness.  Make  a  diagram  showing  the  position  of  the 
thoracic  viscera. 

Familiarize  yourself  with  the  normal  vesicular  sounds  of  the  lungs. 
Auscultate  over  the  bronchi  and  trachea. 

3.  Stethography.— Adjust  a  stethograph  to  the  chest  of  the  subject 
while  he  is  (juietly  sitting  beside  a  table  (see  Fig.  84).  Allow  a  recording 
drum  to  register  the  respiratory  movements  over  the  record  of  a  Jaquet 
chronograph.  Ask  the  subject  to  take  two  or  three  deep  breaths  in 
quick  succession.     Explain  the  result. 

Record  normal  curves  of  respiration  for  about  twenty  seconds. 
Read  aloud  during  the  next  forty  seconds.  Carefully  note  the  modi- 
fications produced  by  the  voice. 

Ask  the  subject  to  hold  his  breath  after  a  moderate  inspiration. 
The  breaking  point  will  be  reached  in  about  forty  seconds.  Repeat 
after  a  deep  inspiration.  The  breaking  point  will  now  be  reached  after 
about  fifty  seconds.  Repeat  after  having  breathed  forcibly  for  two  or 
three  minutes.  The  brealcing  point  then  occurs  after  two  or  three 
minutes.  Since  the  imperative  demand  to  respire  is  due  principally  to 
the  accumulation  of  carbon  dioxid,  and  only  in  a  lesser  degree  to  the 
scarcity  of  oxygen,  the  breaking  point  cannot  be  much  prolonged  by  the 
previous  inhalation  of  oxj'gen. 

Register  a  normal  curve  of  respiration  for  about  twenty  seconds. 
Drink  half  a  glass  of  water  without  stopping.  Explain  this  modifica- 
tion. 

Record  normal  curves  of  respiration.  Ask  the  subject  to  approxi- 
mate the  tips  of  his  two  index-fingers.  Explain  the  change  in  the  char- 
acter of  the  respiratory  movements. 

Take  tracings  of  the  modified  respiratory  curve  of  laughing,  sneez- 
ing, and  coughing. 

139 


140  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

4,  Influence  of  Carbon  Dioxid. — Compress  the  nostrils  of  the  sub- 
ject and  allow  him  to  breathe  from  and  into  a  rubber  bag  containing 
about  30  liters  of  air.  As  soon  as  the  CO2  has  accumulated  sufficiently 
the  subject  will  breathe  more  rapidly  and  more  deepl}'^  until  his  rate  is 
about  forty  to  the  minute.  Stop  the  experiment  soon  after  the  occur- 
rence of  the  hyperpnea. 

Repeat  this  experiment  after  having  interposed  a  receptacle  of 
1  or  2  liters  capacity  containing  soda-lime  or  sticks  of  sodium  hydrate. 
The  carbon  dioxid  will  be  absorbed,  while  the  oxj^gen  in  the  bag  is  being 
used  up.  Consequently,  there  will  be  no  hyperpnea.  Only  a  few 
minutes  will  be  required  to  establish  this  fact.  ImmecUately  allow  the 
subject  to  breathe  normal  air,  otherwise  the  oxygen  deficiency  will  lead 
to  cyanosis,  frontal  headache,  and  unconsciousness. 

5.  Artificial  Respiration. — Familiarize  yourself  with  the  Sylvester 
and  Schafer  methods  of  artificial  respiration.  Place  the  subject  upon 
his  back  with  the  feet  somewhat  elevated.     Take  a  position  at  the  head 


^^^^^^^^^^^^^^^  ' 

1 

r^ 

cs^ 

Fig.  88. — Position  to  Be  Adopted  for  Effecting  Artificial  Respiration  in  Cases 

OF.  Drowning.     {Sr.haefer.) 

of  the  subject  and  grasp  his  wrists.  Now  bring  the  forearms  against 
the  sides  of  the  chest  and  press  gently  inward  and  downward  against 
the  ribs.  Release  the  pressure,  allowing  the  elasticity  of  the  chest  wall 
to  restore  normal  conditions.  Bring  the  arms  above  the  head  so  as  to 
stretch  the  accessory  muscles  and  to  enlarge  the  chest  still  further. 
Repeat  this  procedure  at  the  rate  of  eighteen  times  in  a  minute  (Syl- 
vester) . 

Place  the  subject  upon  his  ventral  surface  with  a  roller  cushion  under 
the  epigastric  region.  Take  a  position  over  the  legs  of  the  subject,  fac- 
ing his  head.  Place  the  palms  of  your  hands  against  the  posterior  and 
lateral  aspect  of  the  subject's  lower  ribs.  Bring  an  even  and  gentle 
pressure  to  bear  upon  this  region.  Release  the  pressure  so  as  to  allow 
the  elasticity  of  the  chest  wall  to  restore  normal  conditions.  Repeat 
this  procedure  at  the  rate  of  sixteen  to  eighteen  times  in  a  minute 
(Schafer).     What  are  the  advantages  of  this  method? 

Study  the  construction  and  action  of  the  pulmotor.  What  are  its 
advantages  and  disadvantages?     Contrast. 


LESSON  XXVIII 

RESPIRATION   (Continued' 

NERVOUS  REGULATION  OF  RESPIRATION 

1.  Accessory  Movements  of  Respiration.-  Aiicstlu-tizc  a  mammal 
and  continiu'  the  ancstht'sia  Ihruu^liouL  tlic  following  experiments: 
Perform  trj\c'heotomy.  Observe  the  movements  of  the  facial  muscles 
and  note  especially  the  changes  in  the  size  of  the  nostrils  during  inspira- 
tion and  expiration.  Render  these  movements  more  conspicuous  by 
temporarily  occluding  the  rubber  tube  attached  to  the  tracheal  cannula. 

2.  Self-regulation  of  Respiration. — Attach  a  pair  of  bellows  to  the 
tracheal  cannula.  Suddenly  inflate  the  lungs.  Note  the  expiratory 
effort  immediately  ensuing.  Suddenly  deflate  the  lungs  and  observe 
that  the  animal  makes  an  inunediate  effort  at  inspiration.  Explain 
these  results  upon  the  basis  of  the  self-regulatory  function  of  the  vagi 
nerves. 

3.  The  Trigeminal  and  Glossopharyngeal  Nerves. — Apply  a  stetho- 
graph  to  the  chest  of  this  animal  and  register  the  respiratory  movements 
upon  the  paper  of  a  slowly  revolving  kymograph.  Stinmlate  the  nasal 
lining  by  means  of  a  small  plug  of  cotton  attached  to  the  end  of  a  stick 
of  wood.  Note  the  resultant  inhibition  of  respiration  and  forced  ex- 
piratory efforts  (act  of  sneezing).  Enumerate  the  different  nervous 
parts  involved  in  this  reflex.  Stimulate  the  lining  of  the  fauces  and 
plmrynx  in  the  same  manner,  producing  thereby  those  modifications  of 
respiration  which  constitute  the  act  of  coughing.  Trace  the  course  of 
this  reflex. 

4.  The  Larynx. — IVIake  a  median  incision  through  the  skin  covering 
the  region  of  the  larynx  and  hyoid  bone.  Ligate  the  vein  crossing  the 
larynx  and  reflect  the  skin.  Identify  the  thyroid  and  cricoid  cartilages. 
Note  the  movability  of  the  larynx  and  trachea.  Isolate  the  superior 
and  inferior  laryngeal  branches  of  the  vagus  on  both  sides,  and  place 
them  in  loose  silk  ligatures. 

Annotation. — The  superior  laryiifjeal  ner\e  pursues  a  course  transversely  across 
from  the  vagus  nerve,  and  enters  the  hiteral  a.spect  of  the  thyroid  cartihige.  It  is 
the  largest  nerve  of  this  region.  The  inferior  laryngeal  nerve  is  isolated  most 
readily  lielow  the  larynx.  It  piu-sues  a  course  upward  along  the  trachea  to  enter 
the  inferior  aspect  of  the  larynx. 

Cut  across  the  pharynx  between  the  hyoid  bone  and  upper  margin 
of  the  thyroid  cartilage.  Bring  the  tip  of  the  epiglottis  through  the 
incision  and  secure  it  by  means  of  a  pair  of  artery  forceps.  Enlarge 
the  incision  laterally  so  that  the  laiynx  may  be  raised  and  an  unol> 
structed  view  be  obtained  of  its  interior.  Identify  the  true  and  false 
vocal  cords,  the  glottis,  and  the  ventricles.  Observe  the  alterations  in 
the  size  and  shape  of  the  glottis  in  quiet  inspiration  and  expiration. 

141 


142 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


Temporarily  occlude  the  rubber  tube  attached  to  the  tracheal  cannula, 
producing  dyspnea  and  thereby  rendering  these  variations  more  con- 
spicuous. 

Stimulate  the  lining  of  the  larynx  with  a  tuft  of  cotton  fastened  to 
a  wooden  stick.  Note  the  resultant  inhibition  of  respiration  and  the 
forced  efforts  at  expiration  (act  of  coughing).     Compare  these  effects 


Fig.  89. — Lateral  View  of  Larynx 
TO  Illustrate  the  Action  of  the  Crico- 
thyroid Muscle. 

H,  Hyoid  bone;  M,  thyrohyoid  mem- 
branes; PA,  pomum  Adami;  T,  thyroid 
cartilage;  C,  cricoid  cartilage;  Tr,  trachea; 
CT,  cricothyroid  m-uscle;  P,  vertical  plate 
of  cricoid  with  {A)  arytenoid  cartilages 
placed  transversely  upon  its  articulating 
processes;  VC,  vocal  cords;  72,  imaginary 
center  of  rotation  of  cricoid.  When  crico- 
thyroid muscle  contracts,  T  and  C  are 
brought  closer  together,  while  A  is  forced 
away  from  PA. 


Fig.  90.  —  The  Innervation  of  the 
Larynx  (Posterior  View;  One  Side). 
B,  Base  of  tongue;  E,  epiglottis;  A, 
arytenoid  muscles;  CA,  crico-arytenoid 
muscle;  T,  trachea;  V,  vagus  nerve;  SL, 
superior  laryngeal  nerve;  /  and  O,  its  inner 
and  outer  branches;  JL,  inferior  laryngeal 
nerve;  Br,  vagal  fibers  innervating  bron- 
chial musculature. 


with  those  commonly  observed  after  the  entrance  of  a  foreign  body  into 
the  larynx. 

5.  The  Superior  Laryngeal  Nerve.— Place  the  intact  superior  laryn- 
geal nerve  in  shielded  electrodes  and  stimulate  very  briefly.  Analyze 
the  effect  produced  thereby  upon  (a)  the  general  character  of  the 
respiratory  movements,  and  ih)  the  action  of  the  laryngeal  muscles. 

Divide  the  superior  laryngeal  nerve  between  two  ligatures.  Stimu- 
late its  distal  as  well  as  its  central  end  repeatedly,  analyzing  the  effects 
producecj  in  each  case. 


RESPIRATION 


143 


Annotation. — T1m»  superior  Iiiryii<;i'al  nerve  is  eliiefly  Ji  sensory  nerve,  hut  also 
embraces  a  eertain  nuiiiluT  of  motor  fillers  wliich  innervate  tlie  ericothyroicl  muscle. 
Consec|uently,  the  stimulation  of  the  intact  nerve  must  give  rise  to  an  inliihitifin  of 
respiration  and  forctnl  expiratory  efforts,  and  secondly,  to  an  apjiroximation  of  the 
cricoid  and  thyroid  cartilages  and  a  greater  tension  of  the  vocal  cords. 

G.  The  Inferior  Laryngeal  Nerve. — Place  the  intact  inferior  laryn- 
gval  norve  in  shielded  electrodes.  .Stimulate  briefly  and  note  the  effects 
of  the  stimulation  upon  (a)  the  general  character  of  the  respiratory 
movements,  and  (6)  the  action  of  the  laryngeal  nmscl(\s. 

Divide  the  inferior  laryngeal  nerve  between  two  ligatures.  Stimu- 
late its  distal  as  well  as  its  central  end,  and  study  the  effects  (if  any) 
produced  in  each  case. 


B 

Fig.  91. — Diagrvm  lLLrsTR.\^TiNG  the  Abduction  and  Adduction  of  the  Vocai.  Cords. 
A,  Abduction:  1,  point  of  insertion  of  the  post,  crico-arytonoid  muscle;  G,  glottis.  B, 
adduction:  2,  points  of  insertion  of  the  lat.  crico-arytenoid  and  thyro-arytenoid  muscles; 
3,  point  of  insertion  of  the  arytenoid  muscles.  The  dot  indicates  the  position  of  the 
center  of  rotation  of  the  arytenoid  caitila^es. 

Annotation. — ^The  inferior  laryngeal  nerve  is  a  motor  nerve,  innervating  the 
muscles  of  the  larynx,  except  the  cricothjToid.  Consequently,  its  stimulation  must 
give  rise  to  peripheral  eflFects  only.  These  consist  chiefly  in  contractions  of  the 
arytenoid  muscles  which  have  to  do  with  the  approximation  of  the  vocal  cords  and 
the  size  of  the  glottis.  In  the  dog  the  innervation  of  this  nerve,  as  well  as  that  of 
the  superior  laryngeal  nerve,  is  unilateral. 

7.  The  Main  Trunk  of  the  Vagus  Nerve. — Expose  both  vagi  nerves 
below  their  superior  laryngeal  branches.  Divide  each  nerve  between 
two  ligatures.  Observe  that  the  rate  of  the  respiratory  movements  is 
now  greatly  reduced,  whereas  their  depth  is  increased.  The  total  gas 
interchange  is  hot  seriously  impaired,  Stmiulate  the  central  end  of 
either  nerve  with  weak,  medium,  and  strong  currents.  Discuss  the 
part  which  the  vagi  nerves  play  in  regulating  the  frequency  and  am- 
phtude  of  the  respiratory  movements,  formulating  a  concise  pictiu'e  of 
the  self-regulation  of  respiration  by  means  of  these  nerves.  Administer 
an  overdose  of  ether  to  the  animal. 


LESSON  XXIX 
RESPIRATION  (Continued) 

LOCALIZATION  OF  THE  RESPIRATORY  CENTER.    PLACENTA.    RESPIRA- 
TION IN  TPIE  FISH 

1.  The  Localization  of  the  Respiratory  Center. — Anesthetize  a  eat 
and  maintain  the  anesthesia  until  the  animal  has  been  killed.  Perform 
tracheotomy.  Place  the  animal  upon  its  ventral  surface.  Make  a 
median  incision  through  the  skin  covering  the  region  of  the  lower  cer- 
vical and  upper  thoracic  vertebrae.  Identify  the  spinous  process  of  the 
seventh  cervical  vertebra  and  follow  this  projection  to  the  laminse,  re- 
tracting the  spinal  muscles.  Stop  bleeding  l)y  applying  dry  tampons 
or  by  torsion  and  ligation  of  the  blood-vessels.  Cut  away  the  laminse 
and  process  of  the  seventh  vertebra  until  a  short  segment  of  the  spinal 
cord  has  been  exposed.  With  a  curved  needle  draw  a  loose  ligature 
around  the  cord. 

Apply  a  stethograph  to  the  chest  of  the  animal  and  allow  the  record- 
ing drum  to  register  the  respiratory  movements  upon  a  slowly  revolving 
kymograph.  A  sufficienth'  long  normal  record  having  been  obtained, 
raise  the  spinal  cord  and  divide  it.  The  animal  continues  to  respire 
normall}',  showing  thereby  that  this  lesion  does  not  interfere  with  the 
efferent  impulses  to  the  muscles  of  respiration.  Divide  the  students 
into  three  groups,  and  proceed  as  follows: 

Group  A. — Expose  the  spinal  cord  in  the  region  of  the  third  cervical 
vertebra.  Place  a  loose  hgature  around  it,  and  divide  it  after  a  short 
normal  tracing  has  been  taken.  The  respiratory  movements  cease 
almost  immediately,  owing  to  the  fact  that  the  transection  has  separated 
the  nuclei  of  the  respiratory  nerves,  principally  those  of  the  phrenic 
nerves,  from  the  respirators^  center.  The  latter,  therefore,  must  lie 
above  this  section. 

Group  B. — Make  a  median  incision  through  the  skin  covering  the 
occiput.  Advance  in  the  direction  of  the  foramen  magnum.  Enlarge 
the  opening  until  a  clear  view  of  the  region  of  the  pons  is  obtained. 
Divide  the  latter  structure  transversely  above  the  medulla  oblongata. 
Since  the  animal  continues  to  breathe,  the  principal  center  of  respiration 
must  be  situated  below  this  level. 

Group  C. — Make  a  median  incision  through  the  skin  covering  the 
occiput.  Palpate  this  region  until  a  depression  in  the  vertebral  column 
is  clearly  felt  through  which  it  is  possible  to  reach  the  medulla  directl}'. 
Pierce  this  structure  with  a  pointed  instrument.  Respiration  ceases 
immediately. 

Compile  the  results  of  the  three  groups  of  students  and  draw  con- 
clusions regarding  the  location  of  the  respiratory  center. 

10  145 


14(5  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

2.  The  Placenta. — Procure  a  placenta.  Wear  rubber  gloves  or 
handle  this  organ  only  with  instruments.  Study  its  appearance  and 
draw  a  diagram  to  illustrate  its  position  in  the  uterus.  Divide  the 
umbilical  cord  and  identify  its  constituent  blood-vessels.  Observe  the 
character  of  the  outer  and  inner  surfaces  of  the  placenta.  Note  that  the 
umbihcal  vessels  complete  their  subdivision  before  the  substance  of  the 
placenta  is  reached.  Follow  a  cluster  of  vessels  and  separate  the  tissue 
suppHed  by  them  from  the  tissue  supplied  by  neighboring  groups  of 
vessels.  Suspend  the  fringed  tissue  so  isolated  in  a  beaker  filled  with 
water.  By  this  means  one  may  reproduce  the  conditions  normally 
existing  in  this  organ,  the  water  representing  the  maternal  blood  with 
which  the  fetal  blood  is  in  diffusion  relation. 

3.  The  Respiratory  Movements  in  Fishes. — Carefully  study  the 
opening  and  closing  of  the  gill  plates.  What  is  the  relation  between 
this  movement  and  the  movements  of  the  floor  of  the  mouth?  Draw 
diagrams  to  show  the  parts  involved  in  these  movements.  Show  the 
position  of  the  maxillary  and  bronchostegal  valves  during  inspiration 
and  expiration. 


LESSON  XXX 
RESPIRATION  (Continued) 

THE  CIRCULATION  IN  THE  LUNG  OF  THE  FROG.  PHENOMENA  OF 
INFLAMMATION.  EFFECT  OF  CHANGES  IN  INTRATHORACIC 
PRESSURE  UPON  THE  LESSER  CIRCUIT 

1.  The  Lung  of.  the  Frog.^Pith  a  frop.  Open  its  jaws  widely,  and 
draw  a  small  curved  needle  and  silk  thread  through  the  soft  tissues 
around  the  orifice  of  the  trachea.  Insert  the  end  of  a  straight  glass 
cannula  in  the  tracheal  orifice  and  secure  it  by  means  of  the  ligature. 
Attach  a  short  piece  of  rubber  tubing  to  the  cannula.  Open  the  ab- 
dominal cavity  of  the  frog  widely.  Blow  air  gently  through  the  can- 
nula until  both  lungs  have  been  fully  inflated.  Kink  the  rubber  tube 
and  apply  a  cHp.  Remove  both  lungs  with  the  heart  and  suspend  them 
until  thoroughh'  dried. 

Transilluminate  them.  Note  the  large  central  cavity  in  each  as 
well  as  the  indi\'idual  alveolar  spaces  along  the  wall.  Cut  each  lung  in 
half  and  inspect  its  interior. 

2.  The  Capillary  Circulation  in  the  Frog's  Lung. — Pith  a  frog  with- 
out losing  any  blood.  Block  the  opening  by  means  of  a  pointed  piece 
of  match.  Proceed  as  has  been  described  in  paragraph  1,  imparting  to 
the  lungs  a  moderate  degree  of  inflation.  Raise  one  lung  out  of  its  cavity 
and  place  it  upon  the  glass  fitted  in  the  orifice  of  a  plate  of  cork,  such  as 
has  been  described  upon, page  99. 

Place  a  cover-slip  upon  the  upper  surface  of  this  lung  and  apply 
gentle  pressure  to  flatten  the  latter.  Study  the  blood  flow  under  the 
low  and  high  powers  of  a  microscope. 

Examine  a  preparation  of  injected  pulmonary  capillaries  under  the 
microscope. 

3.  Phenomena  of  Inflammation. — Allow  a  drop  of  a  dilute  solution 
of  mustard  to  be  drawn  by  capillarit}'  under  the  glass  covering  the  sur- 
face of  this  lung.  Study  the  resultant  phenomena  of  inflammation  as 
exemplified  b}-  changes  m  the  circulation,  viz.,  the  relaxation  of  the 
capillaries,  the  retardation  of  the  flow,  the  greater  vascularity  of  this 
part,  the  gradually  increasing  numbers  of  white  blood-cells,  the  fixa- 
tion of  these  cells  to  the  walls  of  the  vessels,  and  their  final  migration 
into  the  neighboring  tissues. 

4.  Effect  of  Variations  in  Intrathoracic  Pressure  Upon  the  Blood- 
flow  Through  the  Lungs. — With  the  help  of  the  apparatus  represented 
in  Fig.  92  studj-  the  effect  of  the  inspiratory  increase  and  expiratory 
decrease  in  intrathoracic  pressure  upon  the  blood-flow.  The  large 
orifice  of  a  bell-jar  is  closed  with  a  rubber  membrane.     To  its  central 

147 


148 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


area  is  attached  a  metal  plate  and  ring,  so  that  the  membrane  as  a  whole 
may  be  lowered  and  raised.  The  upper  orifice  of  the  bell-jar  is  closed 
by  means  of  a  rubber  cork  bearing  a  relatively  narrow  inlet  tube.  This 
chamber  is  traversed  b}'-  a  horizontal  tube  of  very  soft  rubber,  draining 
a  receptacle  filled  with  water. 

Allow  the  water  to  flow  steadily  through  this  tube.  Then  lower 
the  rubber  membrane  (diaphragm),  thereby  decreasing  the  pressure  in 
the  glass  compartment  (intrathoracic  pressure).     Note  that  the  "pul- 


FiG.  92.— Device  to  Illustrate  the  Influence  of  the  Respiratory  Movements 
UPON  THE  Flow  of  the  Blood  through  the  Pulmonary  Blood-vessels.  (Hering.) 
A,  Bell  jar;  B,  rubber  membrane  closing  it;  V,  soft-rubber  pouch  to  imitate  the  pul- 
monary blood-vessels;  GH,  arrangement  for  forcing  water  through  V  under  a  constant 
pressure;  j,  manometer  connected  with  "intrapleural  space."  On  inspiration,  pro- 
duced by  moving  the  rubber  membrane  downward,  the  intrapleural  pressure  is  decreased. 
This  gives  rise  to  an  aspiration  which  tends  to  pull  the  wall  of  V  outward,  facilitating 
the  flow  from  G  to  H. 


monary  blood-bed,"  as  represented  by  the  thin  rubber  tube,  is  now  large, 
allowing  a  free  through  flow.  The  opposite  effect  is  produced  by  rais- 
ing the  diaphragm.  The  caliber  of  the  pulmonary  blood-vessels  is  then 
(lccr(>ased  and  the  pulmonary  resistance  increased. 

.5.  Effect  of  Decreased  Atmospheric  Pressure. — Place  a  mouse  under 
the  bell-jar  of  an  ordinary  air-pump.  Allow  the  pressure  existing  within 
this  compartment  to  be  recorded  by  means  of  a  mercury  manometer 
connected  with  the  suction  tube  of  the  pump.     Apply  suction,  lowering 


RESPIRATION  149 

the  pressure  gradually  to  oiic-lialt'  aiul  one-third  of  an  atmosphere 
(700  nun.  ?Ip;).  Under  normal  coiidilions  oxygen  exerts  a  pressure  of 
20.94  per  cent,  of  an  atmosphere  or  about  lo3  mm.  Hg.  At  10  per 
cent,  (one-half  of  an  atmosphere)  the  animal  will  l>ecome  restless  and 
dyspneic,  and  at  7  per  cent,  (one-third  of  an  atmosphere)  lose  conscious- 
ness and  die.  This  pressure  corresponds  to  the  pressure  prevailing  at 
an  altitude  of  30,000  feet. 


LESSON  XXXI 

RESPIRATION  (Concluded) 

ELIMINATION  OF  CARBON  DIOXID  AND  CONSUMPTION  OF  OXYGEN 

1.  The  Elimination  of  Carbon  Dioxid  and  Water.—  Kxliulc  repeatedly 
through  a  ji;lass  tube  into  a  beaker  lilled  with  lime-water.  Explain  the 
resultant  turbidity. 

Procure  a  4-ouncc  Woulffc  bottle  with  three  necks  and  the  necessary 
delivery  tubes  and  stoppers;  three  5-inch  calcium  chlorid  tubes  with 
side  tubes  and  perforated  stoppers;  a  (Jeissler  l)ull)  with  KOH  and 
C'aCb  tubes,  two  small  flasks  with  stoppers,  and  two  glass  tubes;  a 
2-liter  bottle  in  which  the  animal  is  placed ;  and  two  8-Hter  bottles. 

The  tubes  containing  the  calcium  chlorid  should  be  put  in  the  diy- 
ing  oven  at  a  temperature  of  100°  to  120°  C.  for  several  hours.  They 
arc  then  cooled  in  a  desiccator.  Weigh  two  of  them,  marked  e  and  /. 
The  Woulffe  bottle  and  Geissler  bulbs  are  filled  with  a  50  per  cent, 
solution  of  KOH.  To  the  latter  is  attached  the  CaCh  part  and  rubber 
connecting  tubes,  which  are  then  clamped.  The  whole  is  weighed. 
The  two  flasks  h  and  h  are  filled  with  a  strong  solution  of  Ba  (0H)2. 
Weigh  the  bottle  d  into  which  the  animal  is  to  be  placed  later  on. 
Connect  these  parts  and  fill  one  of  the  siphon  bottles  (8  Uters).  Arrange 
the  other  {k)  at  a  distance  of  1  m.  below  the  filled  one  (i). 

Place  a  white  rat  into  the  2-liter  l)ottle  and  weigh.  Connect  this 
bottle  with  the  others.  Start  the  siphon.  Adjust  the  distance  of  the 
siphon  bottles  so  as  to  give  a  sufficient  ventilation  to  the  animal  (indi- 
cated by  its  rate  of  respiration).  When  the  upper  bottle  has  been 
nearly  emptied,  clamp  the  tube  connecting  it  with  the  adjoining  flask 
and  quickly  put  the  second  (now  filled)  bottle  in  its  place.  Remove 
the  clamp,  and  again  siphon.  Continue  this  procedure  for  about  one 
hour. 

At  the  end  of  this  period  clamp  the  siphon  tube,  turn  the  stoppers 
of  the  CaCla  bottles,  and  disconnect  the  tubing.  Weigh  tubes  d,  e, 
f,  and  g.  Obviously,  parts  a,  h,  and  c  remove  the  HoO  and  CO2  from  the 
air  supplied  to  the  animal,  whereas  parts  e,  f,  and  g  collect  the  H2O  and 
CO2  given  off  by  the  animal  in  the  course  of  this  experiment.  By  weigh- 
ing these  parts  before  and  after  this  test  a  means  is  provided  for  deter- 
mining the  amount  of  these  excreta. 

Determine  the  loss  in  weight  suffered  by  the  animal  during  this  test. 
Ascertain  how  much  H2O  and  CO2  left  the  animal  during  this  period. 
Do  these  amounts  correspond  to  the  loss  in  weight  of  the  animal? 
Explain. 

2.  The  Consumption  of  Oxygen. — Fill  the  pressure  tube  B  with  a 
solution  of  potassium  pyrogallatc,  made  bj^  mixing  2  parts  of  a  25  per 

151 


152 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


cent,  aqueous  solution  of  KOH  and  1  part  of  a  5  per  cent,  aqueous 
solution  of  pyrogallic  acid.     The  air  must  be  analyzed  as  it  passes  into 


KOH      BaiOH).    CaCk        ^""««'       CaCk    CaClt       j^amOiCli 


Fig.  93. — Appaeatus  for  Estimating  the  CO2  and  H2O  of  the  Expired  Air.     (Hall.) 

the  apparatus  represented  in  Fig.  93  and  again  as  it  leaves  the  siphon 
bottle.     To  accomplish  this  end  fill  the  gas  buret  A  with  water  by 

-JB 


Position  1.  Position  2.  Positions 

Fig.  94. — Gas  Burets  for  Determination  of  Oxygen.     (Hall.) 

suction.     Connect  its  upper  end  with  tube  K  of  the  respiration  appa- 
ratus (Fig.  93),  and  allow  the  siphoned  air  to  displace  the  water  in  the 


RESPIRATION  153 

buret.  Turn  the  stop-cocks  upon  its  two  ends,  and  connect  its  lower 
entl  with  the  rubber  tube  of  the  pressure  bottle  B,  containing;  the  potas- 
sium pyrof!;allate.  Expel  th(^  air  from  the  eomieetiiiK  tube  and  turn 
the  three-way  stop-cock  so  that  the  pyro{z;allate  may  flow  into  the  buret. 
Raise  the  pressure  tube  and  finally  clamp  the  connecting  tube  close  to 
the  l)uret.  Turn  the  buret  repeatedly  (ten  minutes)  and  open  the 
clamp,  allowing  the  potassium  pyrogallate  to  take  the  place  of  the 
absorbed  oxygen.  Then  remove  the  clamp,  but  allow  the  tubes  to 
remain  in  connection  for  another  ten  minutes.  At  the  end  of  this  period 
adjust  the  level  of  the  solution  in  the  buret  to  the  level  of  the  solution 
in  the  pressure  tube.  Take  the  reading.  Analj'ze  the  oxygen  content 
of  the  normal  air.  Sul)tract  the  amount  of  oxygen  of  the  respired 
air  from  that  found  in  the  noi-mal  air.  The  result  corresponds  to  the 
amount  of  oxygen  consumed  by  the  animal. 


LESSON  XXXII 
THE  NERVOUS  SYSTEM 

REFLEX  ACTION 

1.  Histologic  Study  of  Different  Neurons. — Examine  under  the 
microscope  motor  neurons  from  llie  cerebral  cortex,  cells  of  Purkinje 
from  the  cerebellum,  motor  cells  from  the  anterior  horn  of  the  spinal 
gray  matter,  and  sensoiy  cells  from  the  spinal  ganglion.  Draw  a  dia- 
gram of  each. 

Orient  yourself  regarding  the  principal  tracts  of  the  spinal  cord, 
the  formation  of  the  spinal  roots  and  their  function,  and  other  data  of 
general  interest. 

2.  Dissection  of  the  Nervous  System  of  the  Frog.— Kill  a  frog  with 
ether.  ^lake  a  median  incision  tlnougii  the  skin  covering  the  skull 
cap.  Hold  the  scalpel  slantingly  and  perforate  the  bone  about  midway 
between  the  eyes,  taking  care  not  to  penetrate  too  deeply.  With  a 
pair  of  small  forceps  cut  away  the  bone  around  the  perforation,  enlarg- 
ing the  opening  considerably.  Having  uncovered  the  white  cerebral 
hemispheres  and  olfactory  lobes,  dissect  backward  until  j'ou  have 
brought  into  view  the  rounded,  grayish  optic  lobes  or  corpora  bigemini. 
The  cerebellum  is  rudimentarj^  and  occupies  a  position  in  front  of  these 
bodies.     Identify  the  optic  nerves. 

Expose  the  entire  spinal  cord  by  breaking  away  the  vertebra?  along 
the  dorsal  aspect  of  the  animal.  Identify  the  spinal  nerves  and  spinal 
roots. 

3.  Reflex  Action. — Pith  a  frog  and  destroy  its  brain  (not  the  spinal 
cord).  Suspend  the  animal  from  a  stand  over  a  plate.  Pinch  the  toes 
of  one  foot  with  the  forceps.  Observe  that  the  foot  is  withdrawn  from 
the  seat  of  the  stimulation  by  muscular  activity. 

Produce  this  reaction  by  immersing  the  foot  in  a  weak  solution  of 
acetic  acid.  Repeat  by  applying  the  electrodes  to  the  sole  of  the  foot 
and  stimulating  with  a  brief  tetanic  current  of  moderate  strength. 

Destroy  the  spinal  cord  with  a  wire.  Repeat  the  electric  excitation 
and  observe  whether  or  no  the  different  impulses  so  generated  still 
induce  motor  response's.  Draw  conclusions  regarding  the  part  played 
by  the  spinal  cord  in  this  reaction. 

Annoiation. — The  solution  of  acetic  acid  should  be  weak,  possibly  3  drops  of 
glacial  acetic  acid  to  about  20  c.v.  of  water.  Strengthen  it  in  case  it  should  fail  to 
stimulate.  Immerse  the  foot  in  clean  water  after  every  stimulation.  When  the 
electric  current  is  employed  as  a  means  of  inducing  reflex  action,  differentiate  sharply 
between  the  local  nniscular  contractions  and  those  co-ordinated  general  contractions 
which  eventually  cause  the  removal  of  the  foot  from  the  seat  of  the  stimulation. 

In  order  to  save  material  the  student  may  omit  destroying  the  spina!  cord 
with  the  wire.     This  procedure,  as  may  l)e  surmised,  destroys  the  spinal  reflex  ac- 


156 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


tions,  because  it  jji-oduces  a  break  bet\Yeen  the  afferent  and  efferent  arcs  of  the 
reflex  circuits. 

4.  Localization  of  the  Reflex  Center  for  the  Hind  Legs. — If  the 
spinal  cord  has  not  been  destroj^ed  in  the  frog  used  for  Experiment  3, 
this  animal  may  now  be  employed  for  the  following  test:  Suspend  the 
brainless  frog  in  the  usual  way.  Open  its  abdominal  and  thoracic  cav- 
ities and  remove  the  viscera.  Identify  the  vertebral  column  with  its 
nine  vertebrae.  Produce  a  reflex  by  stimulating  the  sole  of  the  foot 
electrically.  Now  make  a  transverse  cut  between  the  second  and  third 
vertebrae.     Test  the  reflexes  again.     Cut  between  the  third  and  fourth 


Fig.  95. — Diagrammatic  Representation 
OF  THE  Brain  of  the  Frog. 
ON,  Olfactory  nerves;  OL,  olfactory 
lobe;  C,  cerebrum;  T,  tween  brain;  OpL, 
optic  lobes;  Cc,  cerebellum;  M,  medulla; 
Co,  spinal  cord.  The  cranial  nerves  are 
indicated  by  Roman  numerals. 


Fig.  96. — Diagram  to  Show  the  Posi- 
tion OF  THE  Reflex  Centers  in  the 
Spinal  Cord  of  the  Frog. 

BC  and  BN,  Brachial  center  and 
nerve;  A,  center  for  the  parts  of  the  trunk; 
SC  and  »SA'',  sciatic  center  and  nerve.  The 
numbers  indicate  the  different  vertebrae. 


vertebrae  and  again  test  the  reflexes.  Continue  this  process  until  no 
longer  able  to  elicit  this  reflex.  At  which  level  do  you  localize  the 
sciatic  center? 

Annotation. — -The  frog  possesses  nine  vertebrje.  Its  vertebral  coUnnn  ends  at 
the  dorsal  prominence.  From  here  the  tenth  vertebra  or  urostyle  extends  backward 
to  the  tip  of  the  body.  Notice  that  the  three  roots  of  the  sciatic  nerve  enter  the 
cord  at  different  levels,  the  arrangement  being  such  that  a  transverse  cut  made 
t)etween  the  sixth  and  seventh  vertebrae  traverses  the  upper  extent  of  the  sciatic 
center,  destroying  the  reflexes  executed  with  the  help  of  this  nerve. 


5.  Localization  of  Function. — The  same  frog  may  be  used  for  the 
following  test:  Identify  the  three  roots  of  one  sciatic  nerve  and  place 
them  in  loose  ligatures.  Place  the  frog  upon  a  moistened  plate  and 
stimulate  each  root  separately  with  single  induction  shocks  of  very 


THE    NERVOUS   SYSTEM  157 

moderate  intensity.  Divide  them  ami  sliimilatc  the  distal  end  of  each. 
()l)servo  that  they  iimci-vatc  dit'tcrcnt  groups  of  muscles. 

A  similar  localization  of  function  may  ho  detected  in  the  sciatic 
center  itself.  \'ery  fine  needle  electrodes  should  be  used  in  mappinj^ 
out  this  area. 

0.  Summation  of  Afferent  Impulses.^ — Destroy  the  ]>rain  of  a  frog 
(not  the  cord).  Adjust  two  thin  coppei-  wires  to  one  foot  about  1  cm. 
apart  and  connect  them  with  the  secondary  coil  of  an  inductoi'ium. 
Stimulate  with  a  subminimal-refiex  induction  shock,  i.  e.,  with  one  which 
does  not  evoke  a  reflex,  but  may  cause  a  local  muscular  reaction. 
Stimulate  with  two  or  three  of  these  sho(;ks  in  quick  succession,  antl 
observe  the  reflex  action  ultimately  resulting  in  consequence  of  this 
summation. 

7.  Effect  of  Thermal  Stimuli. — Remove  the  wires  from  the  frog  used 
in  ExpcM-iment  G.  Dip  the  foot  at  intervals  into  water  of  10°,  20°, 
and  30°  C.  Which  is  the  most  efficient  stimulus?  Finally,  immerse 
the  foot  in  cold  water,  which  is  then  heated  gradually  until  an  intense 
reflex  is  evoked. 

8.  Spreading  of  Reflexes. — Apply  the  electrodes  to  the  foot  of  this 
frog  and  stimulate  first  with  a  weak  current  and  then  with  a  strong 
current.  Note  that  the  weak  stimulation  gives  rise  to  a  perfectly  local- 
ized reflex,  whereas  the  strong  stimulation  evokes,  in  addition,  move- 
ments of  the  other  leg,  trunk,  and  forelimbs.  In  other  words,  the 
strong  stimulation  causes  the  primary  impulses  to  spread  to  other  reflex 
circuits. 

Hold  the  foot  of  one  leg  between  your  fingers.  Place  a  small  piece 
of  filter-paper  moistened  with  modcratelj'  dilute  acetic  acid,  upon  the 
skin  of  the  ventral  aspect  of  the  thigh  of  the  same  leg.  Observe  that 
the  impulses  so  elicited  eventually  involve  other  reflex  circuits,  caus- 
ing the  opposite  leg  to  be  moved.  Naturally,  if  the  filter-paper  is 
brushed  away  by  these  movements,  this  result  has  a  purely  mechanical 
cause.     Immerse  the  frog  in  fresh  water. 

9.  Reflex  Time. — Suspend  the  frog  in  the  usual  wa.y  and  stimulate 
the  sole  of  one  foot  several  times  wath  weak  and  strong  electric  cur- 
rents. Count  in  each  case  the  number  of  seconds  elapsing  between  the 
moment  of  stimulation  and  the  onset  of  the  reflex  action.  This  interval 
is  the  so-called  reflex  time.  What  is  the  relationship  between  this 
period  and  the  intensity  of  th(>  stimulus. 

10.  Inhibition  of  Reflexes  Upon  Central  Paths. — Expose  and  ligate 
the  sciatic  nerve  of  one  side.  Divide  the  nerve  distally  to  the  ligature. 
Apply  the  electrodes  to  the  central  end  of  this  nerve.  Immerse  the 
foot  of  the  opposite  leg  in  a  weak  solution  of  acetic  acid  and  simulta- 
neously stimulate  the  central  end  of  the  sciatic  nerve  with  a  weak 
tetanizing  current.  Note  the  resultant  inhibition  of  the  reflex.  At 
what  point  of  this  reflex  system  do  the  impulses  from  the  central  end 
of  the  opposite  sciatic  nerve  interfere  with  the  impulses  from  the  foot 
inmierscd  in  the  acid? 


LESSON  XXXIII 

THE  NERVOUS  SYSTEM  (Continued) 
REFLEX  ACTION.     REMOVAL  OF  CEREBRUM 

1.  Inhibition  of  Reflexes  by  Higher  Centers. — Kthorize  a  frog. 
Make  a  median  int-ision  tlirouKii  the  skin  coxcrinfi;  the  skull-cap.  Per- 
forate with  (he  point  of  a  knife  and  enlarfj;e  the  opening  by  means  of  a 
pair  of  foreeps.  Identify  the  eerebral  hemispheres  and  remove  them. 
After  an  interval  suspend  the  frog  and  determine  the  reflex  time  in  the 
usual  way. 

Sprinkle  a  few  cr\'stals  of  sodium  chlorifl  upon  the  upper  surface 
of  the  optic  lobes,  and  again  ascertain  the  reflex  time.  Since  these 
bodies  possess  an  inhibitor  action  upon  spinal  reflex  action,  this  means 
of  stimulation  will  tend  to  lengthen  this  period. 

Remove  both  optic  lobes,  and  again  determine  the  reflex  time. 
Obviously,  their  removal  nmst  destroy  this  inhibitor  influence  and 
intensify  spinal  reflex  action. 

2.  Exaggeration  of  Reflexes  by  Means  of  Strychnin. — Inject  a  drop 
or  two  of  a  0.5  per  cent,  .solution  of  sulphate  of  strychnin  into  the  dorsal 
lymph-sac  of  a  frog.  After  a  few  minutes  stimulate  the  foot  of  this  frog 
mechanically.  Repeat  at  brief  intervals,  noting  the  progressive  char- 
acter of  the  nmscular  seizures.  Blow  3^our  breath  at  the  frog  or  tap 
upon  the  table  upon  which  it  is  resting.  Upon  which  elements  of  the 
reflex  circuit  docs  the  strychnin  exert  its  action? 

3.  Reflexes  in  Man.— Let  the  subject  open  his  mouth.  Touch  the 
uvula  with  the  end  of  an  aseptic  gla.ss  rod.  It  will  rise.  Touch  the 
fauces.  The  response  may  be  either  a  movement  concerned  with  the 
act  of  swallowing  or  the  gagging  reflex,  an  act  tending  to  protect  the 
digestive  tract. 

Make  a  sudden  movement  in  front  of  the  eyes  of  the  subject  as  if 
you  were  going  to  strike  him  in  the  face.  The  eyelids  are  closed. 
Touch  the  outer  surface  of  the  cornea  of  the  subject  with  a  cotton  fiber. 
An  immediate  closure  of  the  eyelids  is  the  result.  In  all  these  instances, 
however,  the  character  of  the  reflex  may  be  modified  vohtionally  (in- 
hibition by  the  cerebrum). 

Shield  the  eye  of  the  subject  for  a  few  seconds  with  your  hand. 
Suddenly  withdraw  the  latter,  allowing  Hght  to  enter  the  pupil.  Ob- 
serve the  decrease  in  the  size  of  this  orifice,  brought  about  by  the  con- 
traction of  the  circular  muscle  cells  of  the  iris  (light  reflex).  Request 
the  subject  to  accommodate  alternately  for  far  and  near  objects.  The 
pupil  is  enlarged  during  far  vision  and  constricted  during  near  vision 
(accommodation  reflex).  Pinch  the  skin  of  the  neck.  The  pupil  will 
dilate  (cihospinal  reflex). 

159 


160         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

A  simple  secretory  reflex  may  be  produced  by  moistening  the 
mucous  lining  of  the  mouth  with  a  few  drops  of  very  dilute  acetic  acid 
or  b.y  chewing  a  piece  of  rubber  or  paraffin. 

The  sneezing  reflex  may  be  elicited  by  touching  the  mucous  lining 
of  the  nasal  cavity  with  a  few  cotton  fibers.  Inhibit  this  reflex  by 
pressing  upon  the  upper  lip  with  the  index-finger. 

4.  Tendon  Reflexes  in  Man. — Cross  your  legs,  allowing  one  leg  to 
hang  perfectly  free.  Let  the  assistant  strike  the  patellar  ligament  of 
the  free  leg  with  the  outer  margin  of  his  hand.  Note  the  contraction 
of  the  quadriceps  muscle  and  the  upward  kick  of  the  leg  and  foot. 
During  this  test  the  subject  should  be  perfectly  inattentive,  otherwise 
cerebral  inhibition  will  result. 

Interlock  the  index-fingers  of  your  hands.  While  you  make  a  forced 
effort  to  separate  these  fingers  let  the  assistant  elicit  the  patellar  reflex. 
Note  that  the  kick  is  now  much  stronger  than  before  (reinforcement  of 
reflexes).     Explain. 

Stand  beside  a  low  chair  with  your  leg  resting  upon  it.  Let  the 
assistant  strike  the  tendo  achillis.  The  foot  will  be  extended,  owing  to 
the  contraction  of  the  gastrocnemius  muscle. 

While  the  ankle-clonus  is  not  observed  in  healthy  persons,  the 
student  should  familiarize  himself  with  the  method  employed  in  eliciting 
it.  The  patient  is  seated  and  rests  his  leg  upon  a  chair  of  equal  height, 
allowing  the  foot  to  project  beyond  its  edge.  Steady  the  leg  with  your 
left  hand  and  with  your  right  hand  suddenly  flex  the  foot  upon  the  leg, 
so  as  to  put  the  tendo  achillis  on  the  stretch.  A  series  of  clonic  con- 
tractions of  the  corresponding  muscles  will  result  in  persons  afflicted 
with  certain  spinal  diseases. 

Another  peculiar  phenomenon  noted  in  certain  spinal  diseases  is 
the  so-called  Babinski  phenomenon.  Under  normal  conditions  the 
tickling  of  the  sole  of  the  foot  results  in  a  flexion  of  the  toes  upon  the 
foot  (plantar  reflex),  whereas  under  certain  abnormal  circumstances  the 
first  toe  may  be  extended  and  the  others  flexed. 

5.  Muscle  Tonus. — Etherize  a  frog  under  a  bell- jar.  When  all 
sensibility  has  been  lost,  open  the  abdomen.  Place  the  sciatic  nerve  of 
one  side  in  a  loose  ligature.  Suspend  the  frog  in  the  usual  way.  Note 
that  the  legs  are  held  in  a  position  intermediate  between  complete  re- 
laxation and  contraction  (tonus).  Divide  the  sciatic  nerve  previously 
placed  in  the  ligature.  Observe  that  the  corresponding  leg  now  assumes 
a  more  dependent  position,  i.  e.,  relaxes  more  completely. 

Remove  the  skin  from  the  normal  leg,  and  again  note  the  position 
of  this  leg.  It  will  now  assume  the  level  of  the  opposite  leg,  the  sciatic 
nerve  of  which  has  been  divided.  Explain  this  result,  making  use  of 
the  contention  that  the  tonus  of  skeletal  muscles  is  dependent  upon 
afferent  stimuli  (k^rivod  from  the  integument, 

6.  Threshold  of  Stimulation. — Pith  a  frog.  Carefully  expose  one 
sciatic  nerve  in  the  thigh.  Determine  the  least  strength  of  tetanizing 
current  which  will  cause  a  spreading  of  reflexes  when  applied  to  the  skin 


THE    NERVOUS   SYSTEM  101 

of  the  foot.  Apply  the  same  stiimilus  to  the  liniik  of  the  sciatic  nerve. 
The  intensity  of  the  stimulus  n'(|uir('(l  to  evoke  reflex  aetion  is  usually 
less  when  appHed  to  the  sense  orj^ans. 

Make  a  median  incision  through  the  skin  eoverinp;  the  dorsal  aspect 
of  this  frog.  Raise  the  skin  and  identify  one  of  the  many  nerve-fibers 
crossing  the  dorsal  lymph-space  to  innervate  the  skin  overlying.  Cut 
out  a  piece  of  skin  al)out  1  cm.  scjuan*,  containing  the  terminals  of  this 
nerve.  Raise  this  skin-tlaj),  but  allow  it  to  remain  in  connection  with 
the  body  by^  means  of  the  nerve.  Determine  the  least  strength  of 
stimulus  required  to  cause  a  reflex  movement  when  applied  to  the  sur- 
face of  this  flap  of  skin  Repeat,  applying  the  electrodes  to  the  afore- 
said nerve.  As  a  rule,  the  threshold  value  of  the  current  will  b(>  found 
to  be  lower  in  the  former  instance. 

7.  Effect  of  Removal  of  the  Cerebrum. — Etherize  a  male  frog  under 
a  bell-jar.  When  completely  insensitive  make  a  median  incision  through 
the  skin  covering  the  skull-caj)  and  perforate  the  skull  with  the  point 
of  a  scalpel.  Enlarge  the  opening  and  remove  the  cerebral  hemispheres 
and  olfactory  lobes.  Note  that  the  junction  between  the  cerebrum  and 
the  optic  lobes  is  indicated  externally  by  an  imaginary  hne  drawn 
through  the  anterior  margins  of  the  ear  drums.  Work  rapidly  but  care- 
fully. Bring  the  edges  of  the  wound  together  by  means  of  two  or  three 
sutures,  and  moisten  the  skin  rci)eatcdly  with  fresh  water.  Allow  the 
animal  to  recover  fully.     Carefully  study  its  behavior: 

(a)  What  is  its  posture?  Pass  your  hand  in  front  of  its  eyes.  Is  it 
made  to  move  thereby?  Repeat  this  test  upon  a  normal  frog.  Com- 
pare. 

(6)  Gently  pinch  the  toe  of  the  decerebrated  frog.  Do  you  note 
any  abnormality  in  its  manner  of  jumping?  Place  the  animal  in  water. 
Is  its  power  of  swimming  affected  in  any  way?  Does  it  retain  its 
upright  position? 

(c)  Place  the  frog  upon  its  back.     Does  it  right  itself  ? 

(d)  Place  the  frog  upon  a  somewhat  roughened  flat  surface.  Tilt 
the  board  gradually  and  note  how  wtII  it  adapts  the  axis  of  its  l)ody 
to  the  surface.  Repeat  this  test  bj'  placing  the  frog  upon  a  small 
Ferris  wheel.  Gradually  turn  the  wheel,  noting  that  the  frog  attempts 
to  reach  the  top  by  moving  against  the  direction  of  the  rotation.  Repeat 
this  test  by  placing  the  frog  upon  a  rotating  surface  arranged  horizon- 
tally. The  long  axis  of  its  body  will  then  be  bent  against  the  direction 
of  the  rotation  (compensator}'  movements  of  equilibration). 

(e)  Hold  a  small  tuft  of  cotton  moistened  with  a  few  drops  of  acetic 
acid  in  front  of  its  nostrils.  The  frog  will  make  protective  movements 
with  its  forelimbs  and  move  away  from  the  seat  of  the  stimulation 
(trigeminal  reflex). 

(/)  Place  a  narrow  board  between  the  frog  and  an  incandescent 
light.  Force  the  frog  to  jump  toward  the  Hght.  It  will  avoid  the 
object  casting  the  shadow  (retinal  reflex). 

ig)  Pass  your  index -finger  over  the  skin  covering  the  dorsal  surface 
11 


162         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

of  this  frog.  Observe  that  the  decerebrated  animal  produces  a  pecuUar 
sound  whenever  touched.  The  same  result  may  be  obtained  by  grasp- 
ing the  frog  in  such  a  way  that  your  thumb  and  index-finger  come  to 
he  laterally  upon  the  abdomen'.  Stimulate  a  normal  frog  in  the  same 
manner.     Compare. 

Annotation.- — The  test  described  last  is  one  of  the  best  means  of  ascertaining  the 
function  of  the  cerebrum.  In  the  normal  animal  the  act  of  croaking  is  imder  the 
control  of  the  cerebral  hemispheres,  i.  e.,  it  is  an  associated  act.  Consequently,  it 
will  be  almost  impossible  to  evoke  it  by  inadequate  stimuli.  The  removal  of  the 
cerebrimi,  on  the  other  hand,  changes  this  complex  act  into  a  simple  reflex.  The 
influence  of  the  higher  centers  having  been  destroyed,  it  may  then  be  evoked  by 
ordinary  stimuli  in  a  reflex  way. 

A  male  frog  may  be  recognized  by  the  cushion-like  thickening  at  the  base  of 
the  innermost  digit  of  the  hand.  Besides,  the  male  rana  esculenta  possesses  a 
bladder-like  resonating  pouch  on  each  side  of  the  mouth. 

Attention  should  also  be  called  to  the  fact  that  an  animal  without  cerebral 
hemispheres  is  incapable  of  "feeling."  The  sensorium  ceases  to  exist  after  the 
removal  of  these  structures,  and  only  the  ordinary  reflex  sensory  mechanism  remains 
behind. 

8.  Influence  of  the  Cerebrum. — Place  a  normal  frog  in  a  basin  filled 
with  water.  Warm  the  water  slowly,  and  note  that  the  frog  will  make 
complex  efforts  to  escape  as  soon  as  the  temperature  of  this  medium 
has  risen  to  about  25°  C. 

Place  a  frog,  the  cerebrum  of  which  has  been  destroyed,  in  cold 
water.  Warm  the  water  to  40°  C,  and  observe  the  reflex  movements 
resulting  in  consequence  of  the  thermal  stimulation.  WTiile  this  ani- 
mal may  escape  from  the  basin,  this  result  is  accidental,  and  is  due 
solely  to  the  reflex  contractions  of  the  muscles. 


LKSSON  XXXIV 
THE  NERVOUS  SYSTEM  (Continued) 

STIMULATION  OF  THE  CEREBRUM.     THE  FUNCTION  OF  THE  ROOTS 
OF  THE  SPINAL  CORD 

1.  Cerebral  Localization. —  Procure  a  pair  of  a(ljusta))l('  clcH'trodcs 
and  coiinec't  (Iumii  with  the  secondary  coil  of  an  inductoriiiin.  Arrange 
the  electric  apparatus  for  stimulation  with  a  quickly  interrupted  cur- 
rent. Anesthetize  a  cat  and  maintain  the  anesthesia  throughout  the 
following  experiments:  Perform  tracheotomy.  Place  the  animal  on 
its  side.  Make  a  median  incision  through  the  skin  covering  the  skull- 
cap, and  separate  the  edges  of  the  temporal  nmscles  from  the  bone 
underneath.  Adjust  a  trephine,  about  1.5  cm.  in  diameter,  to  the 
anterior  area  of  the  right  parietal  bone  at  a  distance  of  0.5  cm.  from  the 
median  line.  Carefully  work  the  trephine  until  it  has  penetrated  the 
skull.  Do  not  press  upon  it  heavily  so  as  not  to  break  through  suddenly, 
piercing  the  substance  of  the  cerebrum.  Remove  the  round  plate  of 
bone  with  a  pair  of  forceps.  Apply  dry  cotton,  and  stop  the  bleeding 
by  pressing  soft  wax  against  the  edge  of  the  cut  bone.  Identify  the 
dura  mater  and  its  blood-vessels. 

Observe  that  the  surface  of  the  dura  rises  with  every  systole  of  the 
heart  and  also  during  inspiration.  Insert  a  thistle  tube  in  the  trephine 
opening.  Fill  it  partly  with  warm  saline  solution  and  connect  it  with  a 
recording  tamliour.  Register  these  pulsations  upon  the  smoked  paper 
of  a  kymograph.  The  w'anial  cavity  is  in  this  way  converted  into  a 
plethysmograph,  registering  the  cardiac  and  respiratory  changes  in  the 
volume  of  the  brain. 

Remove  the  thistle  tube  and  enlarge  the  trephine  opening  by  means 
of  a  pair  of  bone  forceps  until  the  crucial  area  of  the  cerebrum  has  been 
completely  uncovered.  Stop  the  bleeding  by  means  of  wax  and  cotton 
tampons.  Incise  the  dura  mater,  noting  the  escape  of  liquor  cerebro- 
spinalis.  Reflect  the  dura  and  expose  the  surface  of  the  cerebrum  along 
the  crucial  sulcus  (fissure  of  Rolando).  Place  the  animal  on  its  right 
side  and  unfasten  the  left  fore-  and  hind  limbs. 

Using  Fig.  97  as  a  guide,  stimulate  the  surface  of  the  cerebrum  in 
the  vicinity  of  the  crucial  sulcus  with  a  weak  tetanizing  current.  If  no 
results  are  obtained,  increase  the  strength  of  the  current  gradually  and 
lessen  the  depth  of  the  narcosis.  Analyze  the  movements  resulting  in 
consequence  of  the  stimulation  of  these  different  areas. 

2.  The  Function  of  the  Roots  of  the  Spinal  Cord. — Close  the  wound 
by  means  of  a  continuous  sutur(\  Make  a  median  incision  through  the 
skin  covering  the  spinous  processes  of  the  lumbar  v(M-tebra?.  By  means 
of  forceps  separate  the  fascia  and  muscle  tissue  from  these  processes. 

163 


164 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


Stop  bleeding  by  tampons,  torsion,  and  ligation  of  the  blood-vessels. 
Expose  the  laminae  of  several  adjoining  vertebrae.  Cut  through  them 
and  remove  the  dorsal  wall  of  the  spinal  canal  of  this  region.  Take  care 
not  to  injure  the  spinal  nerves. 

Incise  the  dura  mater.  Expose  the  spinal  cord  and  identify  the 
anterior  and  posterior  roots  of  one  of  the  spinal  nerves.  Isolate  these 
roots  and  place  each  in  a  loose  ligature.  Stimulate  each  with  a  weak 
tetanizing  current.  Eventually  tie  these  hgatures,  the  one  upon  the 
anterior  root  close  to  the  cord,  and  the  one  upon  the  posterior  root  far 


Fig.  97. — Diagram  Showing  the  Motor 
Points  in  the  Cerebrum  of  the  Dog. 


Fig.  98. — The  Membranes  of  the  Spinal 
Cord. 
1,  Dura  mater;  2,  arachnoid;  3,  pos- 
terior root  of  spinal  nerve;  4,  anterior  root 
of  spinal  nerve;  5,  ligamentum  dentatum; 
6,  linea  splendens.     {After  Ellis.) 


away  from  the  cord.  Stimulate  the  distal  end  of  the  former  with  a 
weak  tetanizing  current.  Repeat  the  stimulation  upon  the  central  end 
of  the  latter.  Tabulate  the  results,  and  determine  the  direction  of 
conduction  in  each  root. 

Kill  the  animal  by  an  overdose  of  ether.  Remove  a  segment  of  the 
spinal  cord,  noting  the  size  and  shape  of  the  subdural  space,  and  the 
manner  in  which  the  spinal  nerves  are  enveloped  by  dura. 

Remove  the  brain.  Identify  its  different  parts,  and  especially  those 
to  which  attention  has  been  called  in  the  lectures. 


LKSSOX   XXXV 

THE  NERVOUS  SYSTEM  (Concluded) 

REACTION  TIME 

1.  Reaction  to  Touch. — Ananp;o  tho  olcctric  apparatus  for  stimula- 
tion with  siniflc  induct  ion  shocks.  Insci-t  a  sij^nal  and  two  simple  kej'S 
in  the  primary  circuit  of  an  induction  apparatus,  and  connect  a  pair 
of  platinum  electrodes  with  the  secondary  coil.  Arrange  to  record  the 
movements  of  the  signal.  Add  a  tuning-fork.  Tho  latter  should  be 
fastened  to  a  separate  stand  and  be  allowed  to  record  from  left  to  right, 
?".  e.,  against  the  direction  of  rotation  of  the  drum  of  the  kymograph. 
Let  the  subject  hold  the  electrodes  against  his  tongue  with  his  left  hand, 
while  his  right  hand  grasps  the  handle  of  one  of  the  two  keys.  Let  the 
observer  then  spin  the  drum  and  close  the  other  key.  As  soon  as  the; 
subject  feels  the  make  shock,  let  him  break  the  current  by  opening 
his  key.  Draw  ordinates  to  the  curves  and  determine  the  time  which 
has  elapsed  between  the  make  and  the  break  of  the  current.  Repeat 
this  experiment  several  times  and  ascertain  the  average  reaction  time. 


Fi(!.  99. — Re.\ction  to  Touch. 
Record  of  signal  hdow  (hat  of  tuniriK-fork  (^Jti  sec).    S,  Moment  of  stimulation;  R,  mo- 
ment of  reaction. 

Repeat  this  experiment  with  a  stronger  stimulus.  What  relation- 
ship exists  between  the  strength  of  the  stimulus  and  the  length  of  the 
reaction  time? 

2.  Reaction  to  Light. — Arrange  5  dry  cells  in  series,  their  total 
strength  amounting  to  about  7  volts.  Connect  these  cells  with  a  small 
incandescent  lamp  (5  or  6  volts),  a  signal,  and  two  simple  keys.  Ar- 
range to  register  the  movements  of  the  signal  above  the  record  of  a 
tuning-fork  vibrating  in  hundredths  of  seconds.  Let  the  subject  hold 
the  l)ridge  of  one  key  in  the  position  of  closure.  Shield  the  other  key 
and  apparatus  from  the  subject  by  a  large  card])oard.  Let  the  observer 
spin  the  drum  and  suddenly  light  the  lamp  by  closing  the  bridge  of  the 
second  key.  The  subject  should  open  his  key  as  soon  as  he  perceives 
the  light.  Determine  the  average  reaction  time  of  several  tests  of  this 
kind. 

165 


166         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

3.  Reaction  to  Sound. — Arrange  in  series  2  or  3  dry  cells,  a  simple 
key,  a  signal,  a  hammer,  and  a  metal  plate.  Arrange  to  record  the 
movements  of  the  signal  and  of  a  tuning-fork.  Let  the  subject  hold 
the  ke}'  closed.  Let  the  observer  spin  the  drum  and  sharply  tap  with 
the  hammer  upon  the  plate,  thereby  making  the  circuit.  Let  the  sub- 
ject open  the  simple  key  as  soon  as  he  hears  the  sound.  Determine 
the  average  reaction  time  of  several  tests  of  this  kind. 

4.  Reaction  Time  with  Choice. — Arrange  the  electric  apparatus  for 
stunulation  with  single  induction  shocks  and  insert  a  signal  and  two 
simple  keys  in  the  primary  circuit.  Connect  the  secondary  coil  with 
a  rocking  bridge  or  mercury  pole  changer,  and,  in  turn,  each  pair  of 
connectors  with  electrodes.  Let  the  subject  hold  the  electrodes  to  his 
tongue,  one  on  each  side  of  it,  and  instruct  him  to  open  his  key  only 
when  the  right  side  of  his  tongue  has  been  stimulated.  Shield  the 
apparatus  by  a  large  cardboard.  Set  the  rocking  key  for  stimulation 
of  either  side  of  the  tongue.  Spin  the  drum  and  close  your  key.  Re- 
peat several  times,  changing  the  point  of  stimulation,  so  that  the  sub- 
ject is  forced  to  judge  which  side  has  been  stimulated.  Does  choice 
prolong  the  reaction  time? 

5.  Patellar  Reflex  Time. — Let  the  subject  be  seated  and  cross  his 
legs.  Adjust  to  the  thigh  of  the  crossed  leg  a  rubber  cuff,  and  connect 
the  latter  by  means  of  rubber  tubing  with  a  recording  tambour.  Ad- 
just a  tuning-fork  upon  a  separate  stand  and  arrange  it  to  register  its 
vibrations  from  left  to  right,  i.  e.,  against  the  direction  of  rotation  of  the 
drum  of  the  kymograph.  Spin  the  drum  and  tap  the  patellar  ligament 
of  the  subject,  while  he  endeavors  to  reinforce  the  patellar  reflex  by 
simultaneous  efforts.  The  record  of  the  tambour  will  show  two 
oscillations,  namely,  a  wave  due  to  the  blow  upon  the  ligament  and 
one  caused  by  the  contraction  of  the  muscles  of  the  thigh.  Draw  an 
ordinate  at  the  beginning  of  each  wave,  and  determine  the  time  which 
has  elapsed  between  the  moment  of  stimulation  and  the  reaction. 

6.  Reflex  Winking  Time. — Connect  the  upper  eyelid  of  the  subject 
by  means  of  a  fine  thread  and  soft  wax  with  a  recording  lever.  Insert 
a  signal  in  the  primary  circuit  of  an  induction  apparatus,  and  place  the 
writing  point  of  the  signal  vertically  below  that  of  the  recording  lever. 
Allow  a  tuning-fork  to  record  below  the  signal.  Place  upon  the  lower 
eyelid  a  pair  of  stimulating  electrodes.  While  the  drum  is  revolving 
at  a  rapid  rate  stimulate  with  a  single  make  or  break  shock  of  suitable 
strength.  Draw  ordinates  and  measure  the  interval  between  the  mo- 
ment of  stimulation  and  the  moment  when  the  upper  eyehd  began  to 
react. 


LESSON  XXXVI 

THE  SENSE  ORGANS 

CUTANEOUS  AND  MUSCULAR  SENSATIONS 

1.  Histologic  Examination  of  Tactile  Corpuscles.— Place  difForont 
tactile  corpuscles  under  the  low  and  high  powers  of  a  microscope  and 
study  their  structure. 

2.  Touch  Localization. — Touch  the  skin  of  the  hand  of  the  subject 
with  the  pointed  end  of  a  pencil,  his  eyes  being  kept  closed  throughout 
this  experiment.  Let  him  then  place  the  l)lunt  end  of  a  pencil  upon 
the  area  stimulated.  Measure  with  a  millimeter  scale  the  error  made 
by  him.  Repeat  the  foregoing  experiment  upon  the  forearm  and  cheek 
of  the  same  subject. 

Touch  the  skin  of  the  subject  twice  in  quick  succession,  selecting 
for  the  two  stimulations  either  precisely  the  same  point,  or  two  points 
lying  close  to  one  another.  Let  the  subject  state  whether  two  areas 
have  been  stinuilated  or  only  one. 

3.  Touch  Discrimination.^ — By  touching  different  areas  of  the  sur- 
face of  the  hand,  arm,  and  face  with  the  points  of  a  caliper  ascertain  how 


Fig.  100. — Esthesiometer  with  Gu.\rded  Points.     (Stirling.) 

widely  this  instrument  must  be  opened  in  order  that  its  points  may  be 
felt  as  two.  Record  in  millimeters  the  results  for  each  part  stimulated, 
and  compare  them,  paying  special  attention  to  the  relative  sensitiveness 
of  the  lips,  cheeks,  tongue,  and  the  flexor  and  extensor  surfaces  of  the 
arm.  In  the  latter  case  observe  that  the  sensibility  increases  in  the 
direction  of  the  fingers  and  also  in  the  transverse  direction  rather  than 
along  the  longitudinal  axis  of  the  limb. 

4.  Action  of  Cocain.— Press  the  point  of  a  needle  upon  the  tongue 
and  note  the  degree  of  pressure  necessary  to  produce  a  distinct  sensa- 
tion of  pain.  Touch  this  area  with  the  end  of  a  camel's-hair  brush, 
moistened  with  a  4  per  cent,  solution  of  cocain.  What  changes  do 
you  note? 

5.  Aristotle's  Experiment. — Cross  the  right  middle  and  index-fingers 
and  place  them  upon  the  palmar  surface  of  the  left  hand.  Place  a 
small  shot  between  them  and  roll  it  about  in  the  palm  of  the  hand. 
Describe  the  sensation. 

167 


168         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

Cross  the  fingers  in  the  same  way  and  rub  them  against  the  tip  of 
the  nose.     Describe  the  sensation. 

Annotation. — Ordinarily  the  tactile  corpuscles  upon  the  outer  surface  of  the 
index-finger  and  inner  surface  of  the  middle  finger  act  in  unison,  producing  har- 
monious impressions.  If  the  corpuscles  upon  the  inner  aspect  of  the  index-finger  are 
now  brought  in  relation  with  those  upon  the  outer  aspect  of  the  middle  finger,  two 
impulses  must  result  in  consequence  of  the  stimulation  of  dissimilar  tactile  points. 

6.  Peculiar  Phenomena  and  Illusions  of  Touch  and  Pressure. — 
Place  the  cross-section  of  a  tube  against  the  skin  of  the  forearm.  An 
impression  of  a  transversely  oval  object  is  produced  thereby. 

Separate  the  points  of  a  compass  about  2  cm.  and  draw  them  in  a 
straight  line  downward  across  the  skin  of  the  forearm,  wrist,  palm  of 
hand,  and  fingers.  A  sensation  of  a  single  line  opening  up  into  two  is 
produced;  moreover,  these  lines  appear  to  be  more  widely  apart  at  the 
wrist,  to  converge  in  the  palm,  and  to  diverge  toward  the  tips  of  the 
fingers. 

Close  your  eyes,  and  follow  the  circumference  of  a  round  object 
first  with  a  short  rod  and  then  with  a  long  rod,  held  between  your  fingers 
in  the  usual  way.  The  object  will  appear  to  be  much  larger  when  out- 
lined with  the  short  rod. 

Apply  the  points  of  a  compass  simultaneously  to  the  skin  of  the 
subject,  his  eyes  being  closed.  Allow  the  subject  to  obtain  a  clear  im- 
pression of  the  distance  between  the  points.  Apply  only  one  of  the 
points,  and  move  this  point  rapidly  an  equal  distance  across  the  skin. 
In  the  former  instance  the  distance  will  seem  greater. 

Make  a  knot  in  a  coarse  thread  about  30  cm.  in  length.  Allow  the 
subject  to  hold  the  knot  between  the  thumb  and  index-finger  of  his 
right  hand,  his  eyes  being  closed.  Pull  the  thread  through  his  fingers 
first  slowly  and  then  more  quickly.  Is  the  subject  capable  of  estimating 
the  length  of  the  thread? 

Apply  a  comb  to  the  dorsal  surface  of  the  subject's  hand,  his  eyes 
being  closed.  Ask  him  to  indicate  the  length  of  the  comb  actually 
applied.  It  will  appear  shorter  to  him  than  it  really  is.  Draw  the 
same  distance  of  comb  slowly  across  the  surface.  It  will  now  seem  longer 
than  it  actually  is,  because  movement  leads  to  an  exaggerated  sensation 
of  length. 

Draw  the  head  of  a  pin  rapidly  to  and  fro  across  the  skin  of  the  fore- 
arm of  the  subject,  his  eyes  being  closed.  The  subject  will  perceive 
the  motion  some  time  before  he  is  able  to  determine  its  direction. 

Touch  your  forehead  with  your  finger.  The  finger  ''feels"  the  fore- 
head. Rapidly  draw  the  finger  across  the  skin  of  the  forehead.  The 
sensation  will  now  be  referred  to  the  forehead. 

7.  Adaptation  to  Touch  Sensations. — Place  an  object,  such  as  a 
cork,  upon  the  skin  of  the  forearm.  The  initial  sensation  of  pressure 
will  gradually  give  way  to  an  indifferent  sensation. 

Dip  your  index-finger  into  a  tube  filled  with  mercury.     Presently 


THK    SENSE    ORGANS  100 

only  the  sonsation  of  prossuro  at  the  surfaco  of  tho  morcury  will  fomain 
behind;  in  fat-t,  eventually  even  the  latter  will  appear  only  when  the 
finger  is  moved. 

8.  Touch  Sensations  Modified  by  Movement. — Touch  the  skin  of  the 
dorsal  surface  of  the  arm  with  the  tij)  of  \()Ui'  index-finj^er.  Note  the 
quality  of  the  sensation.  Draw  the  finger  slowly  across  this  surface. 
The  sensation  of  touch  is  changed  into  one  of  stroking,  due  in  all  prol)- 
ahility  to  the  activation  of  the  nerve  plexuses  investing  the  roots  of  the 
hail's. 

Feel  an}'  surface  with  the  tip  of  your  index-finger.  Draw  the  finger 
across  the  surface.  Note  that  the  sensation  of  simple  contact  is  now 
amplified  hv  s(Misations  of  motion  and  space. 

9.  Projection  of  the  Sensations  of  Touch. — Hold  a  metal  rod  be- 
tween your  fingers  and  draw  its  end  across  a  roughened  surface.  The 
sensation  will  be  referred  to  the  end  of  the  rod,  i.  c,  be  projected  beyond 
the  skin. 

Dip  the  elbow  in  cold  water.  The  initial  sensation  of  cold  at  the 
point  of  contact  with  the  water  will  soon  give  way  to  a  similar  sen- 
sation in  the  region  innervated  by  the  ulnar  nerve. 

10.  Mechanical  Stimulation  of  the  Hot  and  Cold  Spots. — Close  your 
eyes  and  instruct  the  assistant  to  touch  the  tlorsal  aspect  of  your  hand 
with  the  blunt  i)oint  of  a  [x^ncil.  In  certain  areas  you  will  obtain  a 
sensation  of  cold,  and  in  others,  of  heat.  These  spots  arc  separated  by 
areas  in  which  no  sensations  of  temperature  are  evoked. 

Allow  the  assistant  to  draw  the  point  of  a  pencil  slowly  across  the 
surface,  noting  that  distinct  points  of  cold  flash  out.  Sensations  of 
heat  are  not  so  easily  elicited. 

11.  Thermal  Stimulation  of  the  Hot  and  Cold  Spots. — Employ  a 
metal  rod,  about  10  cm.  in  length  and  1  cm.  in  diameter.  Its  pointed 
end  projects  from  a  covering  made  of  rubber  tubing.  Cool  the  rod  in 
ice-water  and  map  out  a  circumscribed  area  upon  the  dorsal  aspect  of 
the  subject's  hand.  Mark  the  cold  spots  with  black  ink.  Warm  the 
rod  to  70°  C.  and  proceed  as  before,  marking  the  warm  spots  in  red  ink. 
Observe  that  the  latter  are  less  easily  found  and  that  their  stimulation 
is  followed  by  a  long(M-  latent  period. 

12.  Chemical  and  Electric  Stimulation  of  the  Temperature  Spots. — 
Apply  objects  of  different  heat-absorbing  power  to  the  skin,  such  as 
wool  and  a  piece  of  metal.  The  latter  feels  colder  because  it  gives  rise 
to  a  greater  loss  of  heat,  thereby  stimulating  the  cold  spots. 

Rub  menthol  upon  the  skin  of  the  hand  or  forehead.  A  sensation 
of  cold  is  obtained  because  this  agent  renders  the  skin  hyperesthetic. 

Identify  a  cold  spot  upon  the  dorsal  surface  of  the  hand.  Employ 
two  electrodes,  one  pointed  and  the  other  flat.  The  former  is  applied 
to  the  cold  spot  and  the  latter  elsew'here  upon  the  hand.  Stimulate 
with  a  weak  induction  current  until  a  distinct  sensation  of  cold  is  ob- 
tained. 

1.3.  "After-images"  of  Temperature. — Place    a  cold  coin  on   the 


170         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

forehead  or  on  the  palm  of  the  hand  for  about  half  a  minute.  Does  the 
sensation  of  cold  continue  even  after  the  coin  has  been  removed,  allow- 
ing the  temperature  of  the  skin  to  rise?  Repeat  this  test  with  a  slightly 
heated  coin. 

14.  Acuity  of  the  Temperature  Sense. — Insert  the  index-finger  in  a 
beaker  filled  with  water  of  30°  C.  Raise  the  temperature  of  the  water 
quickl}'  a  few  tenths  of  a  degree.  How  small  a  difference  are  you  able 
to  perceive? 

15.  Temperature  Contrast. — Place  the  index-finger  of  your  right 
hand  in  water  of  40°  C.  and  the  index-finger  of  your  left  hand  in  water  of 
20°  C.  Wait  a  short  time  until  the  initial  sensations  of  warmth  and 
cold  have  become  less  intense.  Transfer  both  fingers  into  water  of 
30°  C.  Note  that  the  right  finger  feels  cold  because  heat  is  lost  by  it, 
whereas  the  left  finger  feels  warm  owing  to  a  certain  stagnation  of  its 
heat. 

Place  one  index-finger  in  water  of  32°  C.  and  the  other  in  water  of 
45°  C.  Wait  half  a  minute  and  transfer  both  in  water  of  10°  C.  An- 
alyze the  sensation. 

16.  Thermal  Illusions. — Employ  two  disks  of  metal  of  equal  size, 
one  warm  and  the  other  cold.  Place  them  successively  upon  the  skin 
of  the  subject,  whose  eyes  are  closed.  The  cold  disk  will  feel  heavier 
than  the  warm  one. 

17.  Pain  Spots. — Map  out  the  dorsal  surface  of  the  hand  of  the  sub- 
ject with  the  point  of  a  sewing  needle,  noting  the  points  where  a  distinct 
sensation  of  pain  is  perceived. 

18.  Discrimination  of  Weight:  Weber's  Law. — Place  a  small  box 
containing  10  shot  upon  the  palmar  surfaces  of  the  tips  of  the  middle 
and  index-fingers  of  the  subject.  Support  his  hand  at  the  wrist,  and 
ask  him  to  close  his  eyes.  When  he  has  obtained  a  clear  impression  of 
the  weight,  add  or  subtract  shot  until  he  notices  a  distinct  difference. 
Repeat  this  experiment  several  times  and  obtain  a  mean  value  for  the 
number  of  shot  added  or  removed.  Repeat  this  test  with  30  and  50 
shot  respectively  in  the  box.     Tabulate  the  results. 

19.  Relation  of  Weight  to  Area  Stimulated. — Place  two  objects  of 
equal  weight  but  unequal  size  upon  the  dorsal  aspect  of  the  subject's 
hand,  his  eyes  being  closed.  Most  generally,  that  weight  will  be 
thought  to  be  heavier  which  presents  a  greater  surface  to  the  skin, 
i.  e.,  stimulates  the  largest  number  of  tactile  corpuscles. 

Request  the  subject  to  lift  three  cylinders  of  equal  weight,  but 
unequal  size,  and  determine  which  is  the  heaviest.  The  largest  cylinder 
is  usually  thought  to  be  the  heaviest. 

20.  Illusions  Relating  to  Weight. — Lift  an  object  first  rapidly  and 
then  slowly,  and  note  that  its  weight  seems  less  in  the  former  instance. 
Lift  a  certain  weight  with  one  hand  while  clenching  the  other.  The 
weight  seems  lighter  in  consequence  of  the  simultaneous  effort. 

21.  Simultaneous  Movements.^ — Stand  erect  before  a  blackboard. 
Close  your  eyes  and -draw  with  both  hands  placed  at  the  same  height  two 


THE    SKNSE    ORGANS  171 

leaf  pattorns  of  equal  size.  Draw  from  left  to  rip;ht  witii  a  "free  hand" 
motion  of  the  arms,  produced  hy  simultaneous  impulses  directed  eciually 
to  the  two  sides.     Note  th(>  relative  siz(>  and  position  of  the  figures. 

Repeat  this  experiment,  but  place  one  hand  about  12  cm.  above  the 
other.  Obviousl}',  the  nuisde  sense  is  not  well  trained  in  the  averap^e 
person. 

22.  Sensation  of  Motion  at  the  Elbow. — Place  the  forearm  upon  a 
boartl  which  it  is  possible  to  move,  thereby  imitatinj^  the  flexion  of  the 
forearm  upon  the  arm.  Close  the  eyes.  While  an  assistant  raises  or 
lowers  the  free  end  of  th(^  arm-board,  state  when  >'ou  perceive  a  dis- 
tinct motion  of  your  forearm.  How  great  an  angular  movement  is 
necessary  in  order  to  produce  a  sensation  of  motion? 

23.  Paradoxic  Resistance. — Fasten  a  weight  to  a  string  about  2  m. 
in  length.  Close  your  e3'es  and  grasp  the  string  anywhere,  suspending 
the  weight  in  space.  Quickly  lower  the  weight  upon  a  felt  cushion. 
When  contact  is  made  a  definite  sensation  of  resistance  arises,  as  if  the 
hantl  were  supported  by  a  rod. 


LESSON  XXXVII 

THE  SENSE  ORGANS  (Continued) 

TASTE,  SMELL,  HEARING 

1.  Structure  of  the  Taste-buds.— Study  histologic  preparations  of 

the  tast('-l)U(ls. 

2.  Distribution  of  Taste. — Place  a  crystal  of  cane-sugar  upon  the 
tip  of  the  tongue.  Note  that  there  is  a  definite  latency  caused  by  the 
fact  that  solid  substances  cannot  be  tasted.  They  must  first  go  into 
solution. 

Place  a  crystal  of  cane-sugar  upon  the  tip  of  the  tongue  and  another 
upon  its  posterior  area.     Where  is  the  sweet  taste  most  pronounced? 

Employ  a  solution  of  sulphate  of  quinin  (bitter),  a  5  per  cent,  solu- 
tion of  cane-sugar  (sweet),  a  10  per  cent,  solution  of  NaCl  (saline), 
and  a  1  per  cent,  solution  of  acetic  acid  (sour).  Apply  these  solutions 
to  different  parts  of  the  tongue  by  means  of  a  camel's-hair  brush,  and 
observe  wherc^  each  is  tasted  most  acutely. 

3.  "Threshold  Value"  of  Taste.— Moisten  the  tongue  with  ^  tea- 
spoonful  of  a  1  :  1(300  solution  of  cane-sugar.  Do  you  perceive  a  sweet 
taste?  Rinse  the  mouth  and  repeat  the  experiment  with  solutions  of 
the  following  strengths:  1  :  800,  1  :  GOO,  1  :  400,  and  1  :  200.  Which 
solution  produces  the  least  perceptible  sweet  taste?  How  does  the 
acuity  of  taste  in  smokers  compare  with  that  in  non-smokers? 

4.  Taste  Reaction  of  Single  Papilla.— By  using  a  lens  select  a  fungi- 
form papilla  near  the  tip. or  side  of  the  tongue.  Apply  to  it  the  tip  of 
a  camel's-hair  brush  moistened  with  one  of  the  fluids  provided  for  this 
purpose,  xdz.,  weak  anrl  strong  solutions  of  cane-sugar,  sodium  chlorid, 
tartaric  acid,  and  ciuinin.  The  subject  should  indicate  the  taste  which 
he  perceives.  Does  the  papilla  exp(>rimented  with  respond  to  more 
than  one  of  the  agents  used?  Test  other  papillae  in  the  same  manner. 
Explain. 

If  a  papilla  be  found  which  reacts  to  bitter,  paint  it  with  a  solution 
of  cocain.  To  another^  which  is  particularly  responsive  to  sweet,  api)l\- 
a  saturated  alcoholic  solution  of  gymnemic  acid.  Note  the  result  in 
each  case. 

5.  Electric  Stimulation.  Inadequate  Stimuli. — Connect  two  small 
zinc  electrodes  with  a  series  of  4  chy  cells.  Apply  one  of  the  electrodes 
to  the  upper  and  the  other  to  the  lower  surface  of  the  tongue.  An  acid 
taste  will  be  obtained  at  the  positive  and  an  alkaline  one  at  the  negative 
pole.  The  objection  that  electrolysis  is  the  cause  of  these  sensations 
may  be  met  by  employing  non-polarizable  electrodes.  Moreover,  even 
single  shocks  which  cause  practically  no  electrolysis,  give  rise  to  taste 
sensations. 

173 


174         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

6.  Elimination  of  Sweet  and  Bitter. — Apply  a  5  per  cent,  decoction 
of  gymnema  sj^vestris  to  a  limited  area  of  the  tongue.  Twenty  to 
thirty  seconds  later  rinse  the  mouth  thoroughly  and  test  the  taste  with 
the  solutions  used  for  Experiment  2.     What  solutions  remain  effective? 

7.  Structure  of  Olfactory  Cells. — Study  hitologic  preparations  of  the 
olfactory  area. 

8.  Distribution  of  Olfactory  Cells. — Place  a  glass  funnel  over  some 
odoriferous  substance.  Insert  the  tip  of-  the  funnel  first  into  the  lower 
posterior  and  then  into  the  upper  anterior  region  of  the  nasal  cavity. 
Which  region  is  the  more  sensitive  to  the  odor?  Where  is  the  olfactory 
area  located? 

9.  Olfactory  Latency. — Smell  oil  of  cloves  held  close  to  the  nose,  and 
determine  the  time  intervening  between  this  act  and  the  perception 
of  the  sensation.     Give  a  reason  for  this  latency. 

10.  Olfactory  Fatigue. — Smell  tincture  of  camphor,  tincture  of 
iodin,  or  oil  of  cloves  with  one  nostril  until  the  olfactory  cells  have 
been  fatigued.  Note  the  time  it  takes  for  the  fatigue  to  set  in  and 
for  the  acuteness  of  smell  to  be  re-established. 

11.  Qualitative  Changes  Before  Exhaustion. — Inhale  oil  of  cloves 
through  one  nostril  and  observe  the  changes  which  occur  in  the  quality 
of  the  sensation  before  it  ceases. 

12.  "Threshold  Value"  of  Sounds. — Determine  the  greatest  dis- 
tance at  which  the  subject  can  still  hear  the  tick  of  a  watch  placed  on 
the  level  of  his  right  or  left  ear,  the  other  ear  having  been  closed  with 
cotton.  To  avoid  inattention  the  subject  should  shut  his  eyes.  When 
just  at  the  threshold  of  audibility  the  sound  varies  greatly  in  its  intensity. 

Place  the  handle  of  a  vibrating  tuning-fork  upon  the  head.  Note 
the  intensity  of  the  sound,  and  then  remove  the  fork  quickly  before  the 
sound  ceases  completely.  Observe  that  the  change  to  complete  silence 
seems  much  greater  than  the  apparent  low  intensity  of  the  sound  would 
justify. 

13.  Auditory  Fatigue. — Insert  the  ends  of  a  Y-shaped  rubber  tube 
into  the  openings  of  the  ears.  Place  a  vibrating  tuning-fork  upon  the 
tube  in  such  a  way  that  the  sounds  seem  equally  intense  to  both  ears. 
Remove  the  tuning-fork.  After  a  brief  interval  occlude  the  tube  on  one 
side  by  pinching  it,  and  place  the  vibrating  tuning-fork  in  its  former 
position.  When  the  sound  has  nearly  ceased  to  be  audible,  open  the 
pinched  tube.  The  sound  now  appears  to  be  much  stronger  in  the 
rested  ear  than  in  the  other. 

14.  Location  of  Tones. — Place  the  handle  of  a  vibrating  tuning-fork 
upon  the  top  of  the  head.  In  what  part  of  the  head  does  the  sound 
seem  to  be  localized?  Close  one  ear  and  observe  the  change  in  the 
apparent  localization  of  the  sound.     Explain  this  phenomenon. 

Note  the  effects  produced  by  placing  the  tuning-fork  upon  different 
parts  of  the  head. 

Place  the  tuning-fork  upon  the  teeth.  Close  one  ear  and  note  the 
apparent  change  in  the  location  of  the  sound. 


THE   SENSE   ORGANS 


175 


Place  first  the  right  side  and  then  the  left  side  of  your  head  flat 
against  a  pillow.  Do  you  hear  the  sounds  of  your  heart?  In  which 
ear  are  they  perceived  most  clearly?  Give  an  explanation  of  this 
phenomenon. 

15.  Compound  Tones. — Set  in  vibration  a  violin  string  fixed  be- 
tween two  points.  Touch  the  center  of  the  string  with  a  rod.  Observe 
that  the  original  fundamental  tone  is  now  obliterated,  the  lowest  tone 
being  an  octave  higlici-. 

1().  Observation  of  the  Membrana  Tympani  in  Man. — Fasten  the 
reflector  to  Vour  lorehcad,  and  duvet  the  rays  from  a  lantern  into  the 
right  external  auditory  meatus  of  the  subject.  With  your  left  hand  pull 
the  external  ear  l)ackward  and  upwartl,  and  with  your  right  hand  insert 
the  funnel-shaped  tul)(>,  taking  great  care  not  to  injure  the  skin  of  the 
meatus  or  the  membiana  tympani.  Concentrate  the  light  upon  this 
membrane  by  moving  the  reflector  either  nearer  to  or  farther  away  from 


Membrana  flaccida        Posterior  ligament 


Anterior  ligament  — /Jf— 


~-Loy)g  process  of  incus 


-  End  of  manubrium  of  malleus 


Fig.  101. — Membr.\na  Tympani,  as  Seen  with  the  Otoscope.     (Hcustnan.) 

the  ear.  Adjust  the  tube  by  tilting  it,  so  that  a  view  of  the  entire 
membrane  may  be  had.  The  light  should  be  placed  about  60  cm.  from 
the  reflector,  and  the  reflector  about  17  cm.  from  the  membrane. 

Near  the  upper  anterior  border  of  th(>  membrane  will  be  seen  the 
short  process  of  the  malleus,  the  handle  of  the  malleus  extending  down- 
ward and  backward  from  the  short  process.  Locate  the  "umbo," 
which  is  the  most  retracted  area  of  the  membrane,  and  identify  the 
"pars  flaccida,"  the  "pars  tensa,"  and  the  "annulus  cartilagineus." 

17.  Pressure  in  the  Tympanum. — Close  the  mouth  and  nostrils. 
Attempt  to  inspire,  and  swallow.  Note  the  pecuUar  sensation  in  the 
ears  and  the  diminution  in  the  acuity  of  hearing. 

Close  the  mouth  and  nostrils.  Attempt  to  expire,  and  swallow,  A 
similar  sensation  is  produced.  Show  how  these  acts  affect  the  pressure 
in  the  tympanum  and  the  vibratory  quality  of  the  ear  drum. 

18.  Models  of  the  Middle  Ear. — Examine  such  models  as  may  be 
available  for  illustrating  the  action  of  the  ossicles. 


176 


ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 


19.  Observation  of  the  Interior  of  the  Larynx  in  Man. — Place  a 
light  near  the  side  of  the  subject's  head.     Seat  yourself  in  front  of  him, 


Fig.  102. — Diagrammatic  Repre- 
sentation OF  THE  Different  Parts  of 
THE  Ear. 

1,  Pinna;  2,  external  auditory  meatus; 
3,  ear  drum;  4,  middle  ear  containing 
the  ossicles;  5,  eustachian  tube;  6,  vesti- 
bule of  the  internal  ear;  7,  auditory 
nerve;  di^^ding  into  two  branches,  one 
of  which  innervates  the  cochlea,  and  the 
other  the  semicircular  canals;  8,  parotid 
gland. 


Lamp 


Fig.  103. — Diagrammatic  View  of  the 
Internal  Ear. 
1,  Tympanic  cavity;  2,  eustachian 
tube;  3,  incus;  4,  stapes;  5,  vestibule  of 
the  internal  ear  (perilymph);  6,  utricle; 
7,  central  canal  of  the  cochlea;  8,  scala 
vestibuli;  9,  saccule;  10,  endolymphatic 
duct  between  saccule  and  utricle;  11, 
ampulla  of  semicircular  canal;  12,  canalis 
reuniens;  13,  scala  tympani;  14,  helico- 
trema;  15,  fenestra  ovalis. 


Concave  Mirror 


Fig.  104. — Diagram  of  Laryngoscope.     {From  Stewart's  A  Manual  of  Physiology,  Wil- 
liam Wood  &  Co.,  Publishers.) 


and  direct  him  to  incline  his  head  slightly  backward,  to  open  his  mouth, 
and  to  hold  his  tongue  forward  with  the  aid  of  a  handkerchief.  Illumin- 
ate the  pharynx  of  the  subject  by  means  of  a  reflector  fastened  to  your 


TfIR    SENSE    ORGANS  177 

forehead.  Slightly  warm  the  laryngeal  mirror,  and  pass  it  into  the 
subject's  mouth,  carrying  the  miri'or  hoiizonlally  backward  until  its 
back  touches  tlic  base  of  the  u\uia.  Avoid  pressure  upon  the  uvula 
or  contact  with  the  other  soft  parts.  Concentrate  the  light  upon  the 
mirror,  and  tilt  the  latter  until  a  view  is  obtained  of  the  interior  of  the 
larynx,  remembering  that  the  parts  are  seen  inverted  in  the  mirror. 

Identify  the  dorsum  of  the  tongue,  the  slightly  yellowish  e|)iglottis 
with  its  "cushion,"  and  the  glosso-epiglottidean  folds  of  nnicous  mem- 
l)rane.  Identify  the  white  and  shining  "true"  vocal  cords,  the  pink  or 
red  "false"  vocal  cords,  the  arj^epiglottidean  folds,  and  the  mucous 
membrane  covering  the  arytenoid  cartilages  and  cartilages  of  Santorini. 

Observe  th(>  diff(M-(>nces  in  the  form  of  the  glottis: 

1.  During  quiet  ami  forced  respiration, 

2.  While  the  subject  sings  a  low  and  a  high  note,  and 

3.  While  the  subject  sings  th(>  vowel  sounds:  A,  E,  I,  O,  U. 


LESSON   WW  III 

THE  SENSE  ORGANS  (Continued) 
THE  STATIC  AND  DYNAMIC  SENSES 

1.  Dissection  of  the  Ear  of  the  Dog-fish. — Keniove  the  cartilage  be- 
tween the  eyes.  Identify  the  diflerent  parts  of  the  brain.  Proceed 
toward  its  hinder  part,  carefully  reuiovinu;  the  cartilage  from  within 
outward.  Having  reached  one  of  the  semicircular  canals,  remove  its 
upper  wall  as  far  as  possil)le.  Identify  its  membranous  canal  w'ith  its 
ampulla.  Follow  this  canal  until  it  joins  a  meml)ranous  sac,  the  utricle. 
Carefully  expose  the  other  s(Mnicircular  canals.  Open  one  of  the  am- 
pulla and  itlentify  the  crista  acustica,  a  transverse  ridge  carrying  the 
sensory  epithehum. 


Fig.  105. — Position'  of  the  Three  Semicircular  Canals  ix  the  Skill  of  the  Pigeox. 

(Ewalrl.) 

2.  The  Position  of  the  Semicircular  Canals. — Procure  a  human  skull 
in  which  the  semicircular  canals  have  been  exposed,  /.  e.,  the  bone  has 
been  removed,  leaving  only  the  bony  walls  of  the  canals  behind.  In- 
side this  shell  lies  the  membranous  canal  containing  endolymph  and 
invested  by  perilymph. 

Hold  the  skull  in  its  proper  position  and  indicate  by  a  diagram  the 
position  of  these  canals.  How  many  are  there  and  what  position  do 
they  occupy  toward  one  another?  What  planes  in  space  do  they  cor- 
respond to? 

Diagrammatically  represent  the  canals  on  the  other  side  of  the  head, 
and  compare  their  positions  with  those  just  sketched.  Note  that  the 
canals  are  paired,  comprising  the  following  groups:   the  two  horizontal 

179 


180 


ADVANCED    LESSONS    IN    PRACTICAL    PHYSIOLOGY 


ones,  the  right  anterior  and  left  posterior,  and  the  left  anterior  and 
right  posterior. 

Identity  the  ampulla  of  each  canal  and  determine  its  position.  Tilt 
the  skull  in  different  directions,  and  state  which  canals  are  involved  in 
any  particular  movement. 

3.  Model  Illustrating  the  Action  of  the  Semicircular  Canals. — 
Secure  a  model,  such  as  is  represented  in  Fig.  106.  Rotate  the  circular 
glass  tube  containing  water.  Observe  that  the  tube  moves  first  and 
that  at  this  time  the  water  is  still  stationary  The  bristles,  representing 
the  hair  processes  of  the  cells  lining  the  ampulla,  are  deviated  against 
the  direction  of  the  rotation.  Presently  the  water  will  move  with 
practically  the  same  velocity  as  the  tube.  The  hair  processes  then 
extend  straight  into  the  fluid.  On  stopping  the  tube  the  water  will 
continue  to  move  onward,  deviating  the  hair  processes  in  the  direction 
of  its  flow. 


Fig.  106. — Diagrammatic  Representation  of  a  Model  Illustrating  the  Deviation 

OF  THE  Hair  Processes  of  the  Ampulla. 

D,  Disk  rotated  by  hand;  T,  circular  glass  tube  filled  with  water;  B,  bulbular  enlargement 

containing  a  long  camel's-hair  brush,  vertically  placed. 


While  a  free  movement  of  the  endolymph  is  not  possible,  this  schema 
illustrates  at  least  the  principle  involved  in  the  activation  of  the  hair  cells. 

4.  Acuity  of  the  Dynamic  Sense. — Sit  upon  a  revolving  chair.  Close 
your  eyes  and  lift  the  feet  from  the  floor.  Instruct  the  assistant  to 
turn  the  chair  a  short  distance.  What  canals  are  involved  in  this 
movement?  Determine  the  number  of  degrees  through  which  the  rota- 
tion has  taken  place.  Ascertain  the  least  possible  rotation  which  will 
impart  a  sensation  of  movement.  How  would  you  rate  the  acuity  of 
this  sense? 

Bend  your  head  forward.  Repeat  these  tests.  What  canals  are 
involved  in  this  position?  Is  the  sensitiveness  of  these  canals  toward 
this  particular  movement  greater  or  slighter  than  that  of  the  horizontal 
canals? 

5.  Rotation  Effects  in  Mammals. — Place  a  rabbit  in  a  long  and 
narrow  box  which  may  be  rotated  around  its  vertical  axis.  Revolve 
the  box  at  a  moderate  speed  al^out  ten  times  around  its  axis.  Imme- 
diately tilt  the  box  so  that  the  rabbit  slides  out  upon  the  table.    Observe 


THE    SENSE   OROANS  181 

tho  nystagmus,  the  change  in  the  diroction  of  the  long  axis  of  the  ral)- 
bit,  the  change  in  the  position  (;f  its  head,  and  the  compensating  mus- 
cular movements  made  by  it  in  order  to  retain  its  equilibrium.  Do  nut 
rejH'at  this  (experiment  many  times. 

Stantl  erect  and  rotate  a  few  times  around  the  long  axis  of  your 
body.  Repeat  this  test  with  your  eyes  closed.  Analyze  the  peculiar 
phenomena  appearing  when  you  cease  rotating.  In  what  direction  ilo 
the  walls  move?  How  do  you  endeavor  to  counteract  this  impression? 
Since  some  persons  are  unusually  sensitive  to  rotation,  these  experiments 
should  be  performed  with  some  care.  Do  not  rotate  excessively  until 
you  have  determined  by  a  few  rotations  just  how  receptive  you  are. 

Repeat  the  rotation  around  yoiir  vertical  axis  while  you  hold  the 
head  forward.  Retain  this  position  of  the  head  at  the  end  of  the  rota- 
tion. What  canals  are  involved,  and  what  is  th(>  character  of  the  after- 
effects? 

Repeat  the  rotation  around  your  vertical  axis  with  the  head  bent 
forward.  On  ceasing  to  rotate,  raise  the  head.  Analyze  the  after- 
effect. 

0.  Rotation  Effects  in  the  Frog. — Place  a  frog  under  a  bell-jar  upon 
a  revolving  chair.  Turn  the  latter  slowly,  noting  that  the  frog  bends 
its  head  and  body  against  the  direction  of  the  rotation. 

Place  a  frog  upon  a  somewhat  roughened  ])oard.  Tilt  the  board 
and  observe  that  the  frog  bends  its  body,  and  chiefly  its  head,  against 
the  inclination.  Carefully  force  the  frog  to  move  and  make  it  move 
across  the  edge  of  the  gradually  raised  board  and  down  its  opposite 
side. 

7.  Equilibrium  a  Combined  Sense. — Close  your  eyes  and  try  to 
stand  on  one  leg  for  one  minute.  Open  your  eyes  and  repeat  this  test. 
Employ  a  tactile  sensation  in  addition  to  the  visual.  Note  that  you 
can  retain  your  equilibrium  with  greater  ease  if  the  sensations  from  the 
labyrinth  are  augmented  by  other  sensations. 

8.  Railroad  Nystagmus. — While  riding  in  a  street  car  observe  that 
the  eyes  of  the  person  seated  opposite  to  you  are  first  deviated  laterally 
and  are  then  quickly  moved  into  a  median  position.  This  nystagmus  is 
not  of  labyrinthine  origin,  because  it  may  be  made  to  cease  by  accom- 
modation for  a  stationary  object  or  by  shielding  the  eyes. 

9.  Otolithic  Cavity  in  the  Frog. — Etherize  a  frog.  Open  its  mouth 
widely  and  make  an  incision  through  the  membrane  covering  its  roof 
on  the  median  side  of  the  orifice  of  the  Eustachian  tube.  Remove  the 
surface  layer  of  the  bon(>  of  this  region,  thereby  exposing  a  white 
otolithic  mass.  Thoroughly  destroy  this  mass.  Let  this  animal  rest 
for  some  time,  and  then  observe  the  position  of  its  head  and  limbs. 
Rotate  this  frog  and  look  for  compensating  movements.  Does  this 
frog  possess  a  normal  power  of  locomotion?  How  do  its  swimming 
movements  compare  with  those  of  a  normal  frog? 

Destroy  the  otohthic  cavity  on  the  opposite  side,  and  repeat  the 
observations  just  made.     Compare. 


LESSON  XXXIX 

THE  SENSE  ORGANS  (Continued) 

VISION 

1.  Dissection  of  the  Eye. — Procure  an  ox  eye.  Having  itlontificd 
the  hds,  conjunctiva,  and  different  structures  attached  to  the  eyeball, 
isolate  the  optic  nerve  and  cut  away  the  muscles  and  fatty  tissue.  Open 
the  anterior  chainl)er  of  the  eye  by  a  transverse  incision  throufi;h  the 
cornea.  Study  the  physical  characteristics  of  the  aqueous  humor. 
Remove  the  cornea  and  examine  the  iris  and  neighboring  parts.  By 
exerting  a  gentle  pressure  upon  the  outer  coat  of  the  eyeball  force  the 


Fig.  107. — Diagram  of  a  Horizontal  Section  Through  the  Human  Eye. 

C,  Cornea;  A,  antorior  cavity;  P,  po.stcrior  cavity;  L,  Ions;  J,  iris;  T,  conjunctival  sac; 
CL,  ciliary  ligament;  CB,  ciliary  body;  CM,  ciliary  niu.«cle;  OS,  ora  serrata;  CS,  canal  of 
Schlenim;  R,  retina;  Ch,  choroid;  S,  sclera;  OA',  optic  nerve;  A,  retinal  artery;  B,  blind 
spot;  Y,  yellow  spot;  OA,  optical  axis;  VA,  visual  axis;  H,  hyaloid  canal. 

lens  through  the  pupillary  orifice.  Examine  the  lens,  noting  the  degree 
of  convexity  of  its  anterior  and  posterior  surfaces.  Hold  it  over  print. 
Place  it  under  water.  Can  it  be  readily  seen  now?  Explain.  Open 
the  posterior  chamber  widely,  noting  the  differences  in  the  color  of  the 
fundus.  Explain.  Identify  the  optic  papilla  and  obtain  an  idea  re- 
garding the  location  of  the  yellow  spot.  Note  the  characteristics  of 
the  vitreous  humor.  Examine  histologic  preparations  of  the  cornea,  iris, 
lens,  and  retina. 

183 


184         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

2.  Formation  of  the  Image  Upon  the  Retina. — Place  a  fresh  ox  eye 
in  a  watch-glass.  Make  a  small  square  opening  in  its  upper  wall  directly 
behind  the  ciliaiy  body.  Direct  the  pupil  of  this  eye  toward  an  incan- 
descent lamp  (optical  lantern),  the  rays  of  which  have  been  rendered 
parallel  by  the  interposition  of  projection  lenses.  Vary  the  distance 
between  the  light  and  the  eye  until  the  rays  have  been  made  to  inter- 
sect sharply  upon  the  retina.  Place  a  diaphragm  with  an  upright  arrow 
in  front  of  the  projection  lens.  Note  the  condition  of  the  image.  By 
means  of  a  diagram  show  why  the  image  must  be  inverted.  Move  the 
incandescent  lamp  (optical  lantern)  shghtly  in  different  directions  and 
observe  the  direction  of  the  movement  of  the  unage. 

Endeavor  to  thin  the  eyeball  in  the  region  of  its  posterior  pole  by 
removing  the  sclera.  This  means  is  frequently  resorted  to  in  order  to 
obtain  a  clearer  image.  It  illustrates  the  manner  of  focalizing  an 
object  upon  the  ground  glass  of  a  photographic  camera. 

3.  Changes  in  the  Size  of  the  Pupil. — Light  Reflex. — Observe  the 
changes  in  the  size  of  the  pupil  in  a  subject  who  alternately  accom- 
modates for  a  window  and  a  darkened  wall.  Cover  the  eye  of  the  sub- 
ject with  the  flat  of  your  hand  for  a  few  moments.  Remove  the  hand. 
Note  the  constriction  of  the  pupil.  Again  close  one  eye  with  your 
hand  and  observe  the  size  of  the  pupil  of  the  other  eye.  Suddenly  re- 
move the  hand.     Note  that  the  pupil  of  the  other  eye  also  constricts. 

The  cornea  acts  as  a  planoconvex  glass  and  gives  a  larger  size  to  the 
pupil  than  it  actually  possesses.  To  show  this  take  an  ox  eye,  the 
cornea  of  which  has  been  removed.  Place  a  watch-glass  in  front  of  it. 
The  pupil  immediately  appears  larger. 

In  order  to  show  the  movements  of  the  iris  in  your  own  eye  proceed 
as  follows :  With  your  right  eye  look  at  a  uniform  white  surface  through 
a  pinhole  in  a  card,  preferably  at  the  white  shade  of  a  reading  lamp. 
Close  your  left  eye.  Obtain  a  concept  of  the  size  of  the  circular  visual 
field.  Open  the  left  eye.  The  field  becomes  smaller  and  brighter, 
owing  to  the  constriction  of  the  pupil.  Again  close  the  left  eye.  The 
field  gradually  enlarges  and  is  slightly  dulled,  owing  to  the  dilatation 
of  the  pupil. 

Accommodation  Reflex. — Observe  the  changes  in  the  size  of  the  pupil 
in  a  subject  who  alternately  looks  at  objects  near  to  and  far  away  from 
his  eye. 

4.  Changes  in  the  Shape  of  the  Lens. — Look  at  the  eye  of  the  sub- 
ject from  the  side,  observing  the  position  of  the  iris  when  accommodated 
for  a  far  object.  Ask  the  subject  to  accommodate  for  a  near  object. 
Note  that  the  iris  is  forced  forward  into  the  aqueous  chamber,  owing  to 
the  fact  that  the  lens  now  becomes  more  convex. 

Insert  an  ordinary  watch-glass  in  a  tube  of  black  paper,  its  con- 
vexity being  turned  outward.  A  few  centimeters  behind  it  adjust  a 
biconvex  lens.  Hold  the  tube  toward  a  candle,  and  note  the  three 
images  reflected  from  this  system,  viz.,  one  from  the  watch-glass  (cor- 
nea), one  from  the  anterior  surface  of  the  lens,  and  one  from  the  pos- 


THE    SENSE    ORGANS 


185 


terior  surface  of  th(>  lens.     The  first  two  iiiKi;;('s  arc  upright  and   the 
third  inverted. 

In  a  thoroughly  (hirkened  room  phicc  your  eyes  about  2o  cm.  in 
front  and  to  the  h>ft  of  th(>  rinht  eye  of  the  observed  person.  W"\\\\ 
your  left  hand  hold  a  large  cardboard  direcll}-  beside  tiie  right  side  of 


Fig.  108. 


-Reflected  Images  of  a  Candle  Flame  as  Seen  in  the  Ptpil  of  an  Eye  at 
Rest  and  Accommodated  for  Near  Objects.     (IVillianni.) 


your  head.  With  your  right  hand  hold  a  lighted  candle  .somewhat  to  the 
right  of  the  cardboard,  i.  e.,  to  the  right  of  the  visual  axis  of  the  eye  of 
the  observed  person.  Vary  the  position  of  the  candle  and  approach 
the  eye  of  the  subject  until  you  can  clearly  make  out  three  unages, 
viz.,  one  from  the  cornea,  one  from  the  anterior  surface  of  the  lens,  and 


Fig.  109. — Diagram  Illustrating  Course  of  the  Rays  Through  the  Phacoscope. 
A,  Observed  eye;  B,  opening  allowing  acconiniodation  for  near  and  far  objects;  (', 
source  of  light;  D,  observer's  eye;    1,  images  from  cornea;  2,  anterior  surface  of  lens;  3, 
posterior  surface  of  lens. 

one  from  the  posterior  surface  of  the  lens.  The  gaze  of  the  subject 
should  at  this  time  be  directed  straight  ahead  upon  a  distant  object. 
Note  the  position  and  appearance  of  the  images.  Ask  the  subject  to 
accommodate  for  a  n(>ar  object,  but  without  changing  his  visual  line. 
What  changes  do  you  note  in  the  position  and  shape  of  the  images? 


186         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

Draw  conclusions  regarding  the  relative  importance  in  accommodation 
of  these  refractive  surfaces. 

Repeat  these  observations  with  the  help  of  the  phacoscope  (Hehn- 
holtz). 

Annotation. — The  phacoscope  consists  of  a  roughly  triangular  box.  The  ob- 
server's eye  is  placed  in  the  apertiu-e  at  A  and  focalizes  a  far  object  through  apertiu-e 
B.  Orifice  C  contains  two  prisms,  through  which  light  is  reflected  upon  the  eye  of 
the  observed  person.  The  observer  notes  the  images  tlirough  the  orifice  D.  The 
observed  person  then  accommodates  for  the  pin  situated  in  aperture  B  (Fig.  109). 

Since  the  image  from  the  cornea  does  not  change  its  position  or  shape,  the 
cornea  does  not  alter  its  refractive  power.  The  inverted  image  from  the  posterior 
surface  of  the  lens  undergoes  a  very  slight  change,  showing  that  this  refracting 
surface  remains  practically  unchanged.  Contrariwise,  the  image  from  the  anterior 
siu-face  of  the  lens  becomes  more  rounded  and  moves  toward  the  corneal  image. 
This  change  proves  that  this  refracting  siu-face  suffers  the  principal  change  in  ac- 
commodation. 

5.  Wabbling  of  the  Lens. — Gaze  upon  a  Hght  wall  or  ceiling.  Do 
you  notice  black  dots  traversing  the  visual  field  (muscse  vohtantes)? 
If  you  do,  quickly  accommodate  for  a  near  object  and  note  that  the 
spots  execute  a  jerky  lateral  movement.  This  fact  indicates  that  ac- 
commodation relieves  the  tension  under  which  the  lens  is  ordinarily 
held  and  allows  it  to  deviate  somewhat  from  its  optical  axis.  This 
phenomenon  constitutes  the  so-called  wabbling  of  the  lens. 

6.  Formation  of  the  Retinal  Image. — Accommodate  for  a  light  ob- 
ject situated  about  6  m.  from  the  eye.  Hold  the  index-finger  of  your 
right  hand  in  the  visual  axis  of  this  eye.  Draw  a  diagram  to  show 
why  the  finger  appears  indistinct.  Repeat  this  experiment,  but  accom- 
modate for  the  finger.  Draw  a  diagram  showing  why  the  far  object 
is  not  clear. 

Look  at  a  window  through  wire  netting  held  about  25  cm.  in  front 
of  the  eyes.     Later  on  accommodate  for  the  netting.     Explain. 

7.  Scheiner's  Experiment. — Make  two  small  holes  in  a  card  at  a 
distance  of  4  mm.  from  one  another.  Close  one  eye  and  hold  the  open- 
ings in  front  of  the  pupil  of  the  other  eye.  Accommodate  for  a  pin 
held  about  18  cm.  in  front  of  the  eye.  The  pin  is  seen  single.  Now, 
accommodate  for  a  pin  held  at  a  distance  of  60  cm.  from  the  eye.  The 
far  pin  is  seen  single  and  the  near  pin  double.  Close  the  left  opening 
in  the  card  and  observe  which  image  disappears  when  accommodating 
for  the  far  pin  and  which  when  accommodating  for  the  near  pin.  Draw 
diagrams  showing  the  course  of  the  rays,  and  explain  the  peculiar 
blocking  of  the  images  following  the  closure  of  one  or  the  other  of  the 
openings  in  the  card. 

The  psychic  element  in  vision  is  also  clearly  betrayed  by  the  follow- 
ing experiment:  With  the  left  hand  hold  a  card  bearing  a  pinhole  about 
3  or  4  cm.  in  front  of  the  eye.  The  other  eye  should  be  closed  at  this 
time.  With  the  right  hand  bring  the  head  of  a  pin  from  below  into  the 
field  of  vision,  adjusting  the  pin  as  close  as  possible  to  the  pupil.     Note 


THE    SENSE    ORGANS 


187 


that  the  pin  appears  to  enter  the  visual  field  from  above.  Draw  a 
diagram  to  illustrate  the  course  of  the  rays  and  explain  this  peculiar 
phenomenon. 

8.  The  Emmetropic  Eye. — Adjust  the  optical  box  at  a  distance  of 
about  15  cm.  from  the  optical  lantern.  Obtain  parallel  rays  by  placing 
the  tin  tube  containing  the  projection  lenses  in  front  of  the  incandescent 
light.     Lessen  this  bundle  of  light  by  a  diaphragm,  Ix'aring  the  outlines 


Fig.  110. — Optical  Lantern  and  Box.     {Harvard  Apparatus  Co) 

of  the  letter  L.  Close  the  round  opening  in  the  optical  box  by  a  fiat 
piece  of  window  glass  (cornea).  In  the  holder  directl}'  behind  this 
opening  place  a  convex  lens  of  10  cm.  focal  distance  (10  diopters). 
Arrange  the  solid  black  screen  (retina)  near  the  center  of  the  optical 
box.  Close  the  box  with  a  large  plate  of  clean  glass  and  burn  a  small 
amount  of  Japanese  incense  in  the  box.  ]\Iove  the  optical  box  as  well  as 
the  screen  (retina)  until  a  perfectly  clear  image  of  object  L  is  obtained 
upon  the  latter. 


188         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

9.  Circles  of  Dispersion. — j\Iove  the  screen  farther  forward  and  then 
farther  backward.  Note  that  the  rays  now  strike  the  retina  widely 
apart,  i.  e.,  thej^  form  a  dispersion  circle  upon  this  receptor. 

The  same  end  may  be  attained  by  moving  the  lantern  either  farther 
away  or  nearer  to  the  optical  box  (lens).  Draw  diagrams  showing  the 
course  of  tlie  rays  under  these  two  conditions. 

10.  Near  Point. — Again  adjust  the  screen  (retina)  in  such  a  way  that 
the  rays  of  light  emitted  b}^  object  L  are  brought  to  a  sharp  intersecting 
point  (emmetropia) .  With  a  ruler  determine  the  distance  between 
object  L  and  the  lens  of  the  optical  box.  This  distance  constitutes  the 
anterior  focal  distance  of  this  lens  and  indicates  the  position  of  its  near 
point. 

Move  the  lantern  closer  to  the  optical  box.  Observe  that  the  rays 
immediately  pass  into  dispersion  and  finally  leave  the  posterior  surface 
of  the  lens  very  divergently,  illuminating  the  screen  widely.  A  precise 
focal  point  cannot  be  obtained  if  the  object  is  situated  inside  the  near 
point. 

11.  The  Ametropic  Eye.  Hypermetropia,  Myopia. — Construct  an 
eye  that  is  too  short.  To  accomplish  this  end  move  the  screen  2.5  cm. 
in  front  of  the  position  occupied  by  it  when  the  eye  was  emmetropic. 
This  adjustment  simulates  the  condition  of  hi/permetropia  or  far-sighted- 
ness. Theoretically  speaking,  the  focal  point  of  these  rays  lies  behind 
the  screen.  In  order  to  render  this  eye  emmetropic  place  a  convex 
lens  in  front  of  the  aperture  in  the  box  (cornea),  its  strength  being  just 
sufficient  to  converge  the  rays  so  that  they  intersect  upon  the  screen. 
A  lens  of  2  D.  should  accomplish  this  end.  If  a  number  of  different 
lenses  are  available,  other  degrees  of  hypermetropia  may  be  established. 

Construct  an  eye  that  is  too  long.  To  accomplish  this  end  move  the 
screen  a  distance  of  2.5  cm.  behind  the  position  occupied  by  it  in  the 
emmetropic  eye.  Note  that  the  intersecting  point  of  the  rays  now  lies 
in  front  of  the  screen  (vitreous  humor)  and  that  the  rays  then  diverge 
and  strike  the  screen  in  dispersion.  This  condition  is  known  as  myopia 
or  near-sightedness.  In  order  to  correct  this  condition  interpose  a 
concave  lens  in  front  of  the  optical  box  (cornea).  The  entering  rays 
are  thereby  rendered  more  divergent,  so  that  they  are  focalized  exactl}^ 
upon  the  retina.  A  —2  lens  (  —  2D.)  will  accomplish  this  end,  provided 
the  degree  of  myopia  which  has  been  established  is  not  greater  than 
specified. 

Draw  diagrams  to  show  the  manner  of  refraction  in  hypermetropic 
and  myopic  eyes,  and  also  indicate  how  these  errors  may  be  corrected. 

At  the  close  of  this  exercise  replace  every  lens  in  its  proper  paper 
envelope. 


LESSON  XL 

THE  SENSE  ORGANS  (Continued) 

VISION 

1.  The  Ametropic  Eye.  Astigmatism.^ Adjust  the  optical  lantern 
and  box  to  I'oiin  an  onnnotiopic  eye.  Insert  the  diaphragm  with  the 
2  mm.  aperture  in  the  opening  of  the  optical  lantern.  Place  a  beaker 
with  water  directly  in  front  of  the  cornea.  Note  that  the  image  now 
simulates  a  vertical  line.  Close  the  top  of  the  beaker  by  means  of  a 
small  piece  of  cardboard.  Hold  the  beaker  between  your  thumb  and 
index-finger  and  place  it  horizontally  in  front  of  the  cornea.  Note  that 
the  image  now  simulates  a  horizontal  line.  Draw  a  diagram  to  show  the 
course  of  the  refracted  parallel  rays. 

Repeat  the  preceding  tests  by  holding  a  cylindric  lens  in  front  of 
the  cornea,  first  with  its  greatest  curvature  adjusted  in  the  vertical 
direction  and  then  adjusted  in  the  horizontal  direction.  By  this  means 
may  be  imitated  the  conditions  of  "mth-the-nde"  and  "ayainst-the- 
rulc"  regular  astig7}iatism.  It  will  be  remembered  that  the  astigmatism 
which  the  phj'sician  is  usually  called  upon  to  correct  is  due  to  a  faulty 
curvature  of  the  cornea.  In  each  case  move  the  screen  farther  forward 
and  backward  and  note  the  changes  in  the  shape  of  the  image.  Explain 
these  changes  by  means  of  a  diagram. 

By  means  of  a  cj-lindric  lens  establish  the  condition  of  "with-the- 
rule"  astigmatism.  Move  the  screen  so  as  to  obtain  as  distinct  an 
image  as  possible.  Correct  this  condition  by  interposing  in  front  of 
this  cylindric  lens  another  one  of  the  same  refractive  power,  but  ad- 
justed in  such  a  way  that  its  greatest  curvature  comes  to  lie  in  the 
horizontal  plane  of  the  cornea. 

Establish  and  correct  the  condition  of  "against-the-rule"  astigmatism 
in  the  same  manner. 

Explain  the  fact  that  in  the  absence  of  a  faulty  curvature  of  the 
cornea,  all  round  luminous  objects,  such  as  lamps  and  stars,  do  not 
appear  round,  but  as  radiate  figures. 

2.  Chromatic  Aberration.^ — Let  the  rays  from  the  lantern  emerge 
parallel  through  the  2  nun.  aperture.  Hold  a  lens  of  10  D.  about  15 
cm.  in  front  of  the  lantern,  i.  e.,  at  a  distance  greater  than  the  focal 
distance  of  this  lens.  Place  a  white  sheet  of  paper  in  the  path  of  the 
converging  bundle  of  fight  at  a  distance  of  about  15  cm.  from  the  lens. 
Note  the  colors  around  the  margin  of  the  image.  Correct  this  aberra- 
tion by  covering  the  edges  of  tiie  lens  with  a  circle  cut  out  of  cardboard. 
How  is  chromatic  aberration  prevented  in  our  eye? 

Make  a  pinhole  in  a  card  and  place  it  upon  cobalt  glass.  Close  one 
eye  and  with  the  other  gaze  at  a  gas  flame  through  the  pinhole.     The 

189 


190         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGi 

cobalt  glass  permits  only  the  red  and  violet  rays  to  pass.  In  accom- 
modating for  the  red  rays  a  violet  halo  is  obtained  and  on  accommodat- 
ing for  the  violet  rays,  a  reddish  halo. 

On  a  black  background  place  a  strip  of  red  paper  and  one  of  blue 
paper.  The  red  appears  nearer  than  the  blue.  Since  the  red  rays  are 
less  refrangible,  a  greater  effort  at  accommodation  is  required  to  focal- 
ize them.     This  gives  rise  to  an  erroneous  judgment  of  distance. 

Place  a  heart  colored  red  upon  a  bright  blue  sheet  of  paper.  In  a 
room  lighted  only  by  a  candle  hold  the  heart  below  the  level  of  the  eyes 
and  move  it  gently  from  side  to  side.  The  red  heart  will  then  appear 
to  flutter  over  the  blue  background. 

3.  Spheric  Aberration. — Construct  an  emmetropic  eye.  Note  that 
while  the  focal  point  upon  the  screen  seems  perfectly  sharp,  a  close 
observation  shows  that  this  "point"  is  really  drawn  out  backward. 
This  distortion  is  due  to  the  development  of  caustics,  i.  e.,  the  rays  of 
light  traversing  the  marginal  zone  of  the  lens  are  focahzed  somewhat 
behind  those  traversing  its  central  area.  Correct  this  defect  by  cover- 
ing the  peripheral  sphere  of  the  lens  with  a  circle  cut  out  of  paper.  How 
is  spheric  aberration  prevented  in  our  eye? 

4.  Mechanical  Stimulation  of  the  Retina.  Phosphenes.— Shut  one 
eye  and  turn  it  inward.  With  the  point  of  a  pencil  press  gently  upon 
the  outer  surface  of  the  upper  eyeHd.  To  what  part  of  the  field  of  vision 
is  the  yellowish  circular  image  referred.     Explain. 

Place  a  light  in  front  of  the  eyes.  Close  them  and  move  them 
quickly  from  side  to  side.  When  the  eyes  reach  an  extreme  position, 
observe  the  rapidly  disappearing  bluish  spot  surrounded  by  a  yellow 
halo.  Obviously,  this  movement  stimulates  the  retina  around  the 
optic  papilla  in  a  mechanical  way.  Note  that  mechanical  stimuli  are 
inadequate  stimuh.  W^hile  they  produce  visual  sensations,  they  can- 
not give  visual  concepts.  Moreover,  all  retinal  impressions  are  al- 
ways projected  into  the  opposite  visual  field,  i.  e.,  into  that  part  of 
the  field  with  which  that  particular  area  of  the  retina  is  in  functional 
relation. 

5.  The  Field  of  Vision. — Fasten  a  sheet  of  white  paper  60  cm. 
square  upon  a  piece  of  pasteboard  and  make  a  small  cross  mark  about 
30  cm.  to  the  right  of  the  left  margin  of  the  paper.  Let  the  subject 
rest  his  chin  upon  an  iron  support,  and  adjust  the  paper  in  such  a  way 
that  his  right  eye  is  in  a  direct  line  with  the  cross  mark.  Move  the 
verticall}^  placed  paper  close  enough  so  that  he  cannot  look  beyond  its 
edges.  Let  the  experimenter  fasten  a  small  piece  of  white  paper  to  a 
straw,  move  it  horizontally  inward  from  without,  and  mark  on  the  white 
sheet  the  point  at  which  this  object  becomes  clearty  perceptible  to  the 
person.  Determine  in  this  way  also  the  boundaries  of  the  visual  field 
of  this  eye  in  the  vertical  direction,  and  in  two  or  three  intermediate 
directions.  Outline  the  inner  side  of  the  field  in  a  corresponding  man- 
ner. Connect  the  different  pencil  marks  to  form  a  continuous  hne. 
The  visual  field  of  the  left  eye  may  then  be  mapped  out  in  a  similar 


THE    SENSE    ORGANS 


191 


WE}'.     Tho  shoot  of  papor,  Iiowovor,  must  thon  ho  adjustod  in  front  of 
this  eye  and  hoar  a  cross  mark  near  its  rifi;ht  marfi;iii. 

If  a  perimeter  is  availahlo,  the  suhjoct  should  ho  comfortal)ly  seated 
at  a  tahle  with  his  chin  resting  upon  tho  sujjport.  Either  the  right  or 
tho  left  eye  shoukl  thon  ho  focalized  steadily  upon  the  white  dot  in  the 
center  of  tho  somicircl(\  Tho  metal  arch  l)oais  a  sliding  path  in  which 
is  moved  the  oi)joct,  generally  a  small  white  scjuaro,  from  without 
inward,  its  movement  heing  indicated  in  degrees  upon  a  scale  inscrihed 
upon  the  arch.      The  point  at  which  tho  ohjoct  hocomos  first  visihio 


Fig.  111. — The  Perimeter. 


is  then  indicated  upon  a  small  piece  of  paper  upon  which  different 
meridians  have  heen  drawn  out  to  correspond  to  those  of  the  metal  arch. 

Study  the  general  outline  of  the  visual  field  of  each  eye.  Whj^  is 
it  not  round,  hut  oval,  with  its  more  pointed  area  toward  the  nasal  side? 
Do  3"0U  note  any  iiTogularities  in  its  outline  which  cannot  be  ascrihed 
to  a  faulty  technic?  Enumerate  the  causes  which  might  be  held  re- 
sponsible for  such  restrictions  of  tho  visual  field. 

G.  The  Fields  for  Colored  Objects. — Proceed  as  described  in  para- 
graph 5,  but  insert  red,  blue,  and  green  squares  in  the  holder  upon  the 


192 


ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 


metal  arch.  While  the  subject  gazes  fixedh^  at  the  mark  in  the  center 
of  the  arch,  move  these  colors  interchangingly  from  without  inward 
along  the  different  meridians  of  the  eye.  As  soon  as  the  subject  per- 
ceives the  color  clearl}^,  indicate  this  point  in  degrees  upon  the  smaller 
chart.  Eventually,  connect  all  the  points  of  the  same  color  with  one 
another. 


Fig.  112. 


-Perimeter  Chart  to  Show  the  Field  of  Vision  for  a  Right  Eye  When 
KEPT  IN  A  Fixed  Position. 


While  the  results  differ  materially  with  the  saturation  of  the  dif- 
ferent colors,  most  generally  the  red  field  is  the  largest,  then  follows  the 
blue,  and  lastly  the  green. 

7.  Entoptic  Phenomena  Produced  by  the  Tears. — Evoke  a  mild 
hypersecretion  of  lacrimae  by  holding  a  cut  onion  at  some  distance  be- 
low the  eye  or  imitate  this  condition  by  moistening  the  eyelids  with 
fresh  water.  Close  the  eyelids  somewhat,  so  as  to  deepen  the  layer  of 
lacrimae  upon  the  central  area  of  the  cornea.  What  effect  has  this 
upon  refraction  and  the  formation  of  the  retinal  image?  Draw  a  dia- 
gram to  show  how  refraction  is  affected  under  water. 


LESSON  XLI 

THE  SENSE  ORGANS  (Continued) 

VISION 

1.  The  Near  and  Far  Points  of  the  Eye. — Hold  a  pin  50  cm.  from 
your  eyes  antl  move  it  slowly  toward  thciii  until  a  point  has  been  reached 
beyond  which  this  object  no  longer  produces  a  clear  image.  Measure 
the  distance  of  this  point  from  your  eyes  and  determine  whether,  in 
accordance  with  your  age,  it  is  situated  at  a  normal  distance.     Deter- 


FiG.  113. — Ophthalmometer.     {Hardy.) 

mine  the  near  point  for  each  eye.     In  the  emmetropic  eye  the  far  point 
lies  at  the  horizon. 

Select  a  number  of  students  with  abnormal  vision  and  determine 
the  near  and  far  points  in  each.  Ascertain  whether  they  are  far-sighted 
or  near-sighted. 

13  193 


194         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

2.  Detection  of  Astigmatism. — Determine  the  near  point  for  a  pin 
held  vertically  and  one  held  horizontally.  Note  whether  the  distances 
correspond.     If  not,  what  are  your  conclusions. 

Draw  two  lines  5  cm.  in  length  and  intersecting  at  right  angles. 
Each  right  angle  again  bisect  and  each  oblique  angle  again  by  other 
lines,  until  a  radiate  figure  is  obtained.  Interpose  this  figure  at  the 
near  point  of  accommodation.  Note  whether  any  of  these  lines  appear 
blurred.     Explain. 

3.  Measurement  of  Astigmatism. — Carefully  study  the  construc- 
tion of  the  ophthalmometer  (Helmholtz),  and  discuss  the  principle 
involved  in  this  method  of  detecting  and  measuring  astigmatism. 

4.  Visual  Angle. — The  visual  angle  is  the  angle  formed  by  the  lines 
drawn  from  the  two  extremities  of  an  object  through  the  nodal  point 
of  the  eye  (optical  center  of  the  lens).  It  is  situated  7  mm.  behind  the 
cornea  and  15  mm.  in  front  of  the  retina.  Since  these  lines  traverse 
the  nodal  point  unrefracted,  the  size  of  the  retinal  image  may  be  ob- 
tained from  this  projection.  Draw  a  diagram  to  show  that,  in  order 
to  subtend  at  the  same  angle,  objects  must  be  made  increasingly  larger, 
the  farther  they  are  removed  from  the  retina.  Thus,  the  letter  A  seen 
clearly  at  6  m.,  would  have  to  be  ten  times  as  large  at  60  m.  in  order 
to  be  seen  equally  well.  At  a  distance  of  1  m.  this  letter  should  be  1  cm. 
in  height  in  order  to  be  seen  clearly  by  the  emmetropic  eye. 

5.  Snellen's  Test  Tjrpes. — Determine  the  normal  acuity  of  vision 
by  distinguishing  different  letters  subtending  at  an  angle  of  5  degrees. 
If  the  distance  indicated  can  be  exceeded  or  cannot  be  reached,  the 

acuity  of  vision  may  be  expressed  as  =  -j-     In  this  formula  D  stands 

for  the  given  distance,  at  which  the  angle  of  5  degrees  is  subtended,  and 
d  for  the  distance  at  which  the  letters  can  be  recognized. 

Equip  the  ametropic  person  (myopic  or  hypermetropic)  with  lenses 
of  different  refractive  power  until  able  to  recognize  these  letters  clearly. 

6.  Ophthalmoscopic  Examination  of  the  Emmetropic  Artificial  Eye 
by  the  Direct  Method. — Remove  the  projection-lens  from  the  optical 
lantern.  Adjust  the  emmetropic  artificial  eye  for  far  vision  at  zero, 
and  place  it  to  the  left  of  the  lantern  and  on  a  level  with  your  own  eye. 
With  the  right  hand  hold  the  ophthalmoscope  close  to  your  right  eye 
and  about  30  cm.  from  the  artificial  eye.  Make  the  visual  axis  of  your 
right  eye  coincide  with  that  of  the  artificial  eye  by  keeping  your  head 
erect.  Look  through  the  opening  in  the  mirror  and  throw  the  light 
into  the  pupil  of  the  artificial  eye.  Accommodate  your  own  eye  for  an 
imaginary  object  placed  at  some  distance  precisely  behind  the  artificial 
eye.  Gradually  move  your  head  toward  the  artificial  eye  until  the 
mirror  lies  in  the  anterior  principal  focus  of  the  latter,  i.  e.,  about  5  cm. 
in  front  of  the  cornea  of  the  artificial  eye. 

When  the  fundus  of  the  artificial  eye  has  become  visible,  find  the 
optic  disk.     Draw  a  diagram  showing  the  course  of  the  rays  of  light. 
In  case  the  observer  is  myopic  or  hypermetropic,  he  must  first  cor- 


THE   SENSE    ORGANS 


195 


rect  his  error  in  refraction  by  placinp;  a  suital)le  lens  behind  the  opening 
in  the  mirror. 

7.  Ophthalmoscopic  Examination  of  the  Ametropic  Artificial  Eye  by 
the  Direct  Method.— Hciidcr  tlic  arliticial  eye  ametropic  by  pu-siiin^ 
its  two  parts  closer  together  or  by  separating  them  more  widely.  Ex- 
amine its  retina  with  the  ophthahiioscope  hold  at  a  distance  of  from 
30  to  50  cm,  in  front  of  it.  Wiien  the  details  of  the  funchis  have  lx>- 
come  visible,  move  youi'  head  together  with  the  of)hthalmoscope  from 
side  to  side.     In  the  hypermetropic  eye  the  retinal  vessels  will  appear 


Fig.  114. — Loring's  Ophthalmoscope,  with  Tiltixg  Mirkor,  Complete  Disk  of 
Lenses  from  —  1  to  —  S  and  0  to  +  7,  .\nd  Si,"pplement.\l  Quadr.\nt  Containing  = 
0.5  .\ND  ±  16  D.    This  Affords  66  Gl.\sses  or  Combinations  from  +  23  to  —  24  D. 

to  move  in  the  same  direction,  and,  in  the  myopic  eye,  in  the  opposite 
direction.  Having  in  this  way  determined  whether  the  Qyo  is  myopic 
or  hypermetropic,  measure  the  degree  of  tliis  ametropia  in  the  following 
manner: 

Place  the  ophthalmoscope  in  the  anterior  focal  plane  of  the  artificial 
eye,  i.  e.,  5  cm.  in  front  of  its  cornea.  Illuminate  the  pupil  and  accom- 
modate your  own  eye  for  a  distant  point.  If  th(>  artificial  eye  is  myopic, 
place  behind  the  opening  in  the  mirror  concave  lenses  of  different 
strengths,  until  the  lens  has  been  found  which  renders  a  certain  part 
of  the  optic  disk — for  example,  a  peripheral  blood-vessel — perfectly 


196  ADVANCED    LESSONS   IN   PRACTICAL   PHYSIOLOGY 

clear.  If  the  artificial  eye  is  hypermetropic,  use  convex  lenses  instead 
of  concave.  The  focal  power  of  the  lens  which  is  needed  in  order  to 
be  able  to  see  the  fundus  of  the  eye  of  the  subject  clearly,  is  the  lens 
needed  to  overcome  the  ametropia  of  tliis  eye.  In  prescribing  glasses 
for  patients  the  strength  of  the  lens  is  somewhat  exaggerated,  i.  e.,  we 
prescribe  in  hypermetropia  the  strongest  convex  lens  with  which  the 
observer  is  still  able  to  see  the  details  of  the  fundus,  and  in  myopia  the 
weakest  concave  lens.  Why?  Draw  diagrams  to  show  the  course  of 
the  rays  emitted  by  myopic  and  hypermetropic  eyes.  Also  indicate 
how  these  conditions  may  be  corrected  by  the  interposition  of  suitable 
lenses. 

8.  Ophthalmoscopic  Examination  of  the  Artificial  Eye  by  the  In- 
direct Method. — Place  a  convex  lens  of  5  diopters  behind  the  opening 
in  the  mirror  of  the  ophthalmoscope,  and  hold  the  latter  about  30  cm. 
in  front  of  the  artificial  eye.  Interpose  at  a  distance  of  5  cm.  from  the 
cornea  of  the  artificial  eye  a  +20  lens,  held  between  the  thumb  and 
forefinger  of  the  left  hand.  The  rays  which  issue  from  the  artificial  eye 
are  focalized  in  space  after  they  have  passed  through  the  +20  lens. 
This  image  you  study  with  the  aid  of  the  +5  lens.  Draw  a  diagram  to 
show  the  course  of  the  rays  emitted  by  this  eye. 

9.  Skiascopy  or  the  Shadow  Test. — Hold  the  plane  mirror  of  the 
ophthalmoscope  in  front  of  your  eye  and  at  a  distance  of  1  m.  from  the 
emmetropic  artificial  eye.  Throw  a  beam  of  Hght  upon  this  eye.  That 
portion  of  it  which  falls  upon  the  pupil  is  condensed  on  the  retina  and 
forms  here  an  area  of  light  which  moves  in  accordance  with  the  move- 
ment of  the  mirror.  Consequently,  the  same  condition  is  obtained  here 
as  when  Hght  is  reflected  against  a  wall  by  means  of  a  mirror.  Draw 
a  diagram  to  show  the  real  movement  of  the  light  upon  the  retina, 
note  that  its  movement,  as  seen  through  the  pupil,  is  the  same  as  that 
of  the  hght  on  the  face. 

Render  the  artificial  eye  myopic  by  drawing  its  halves  farther  apart. 
Place  the  mirror  at  a  distance  of  1  m.  from  the  eye  and  tilt  it  gently. 
Note  that  the  pupillary  reflection  now  moves  in  a  direction  opposite  to 
that  of  the  mirror.  Move  closer  to  the  eye  until  a  point  has  been  reached 
at  which  it  is  impossible  to  tell  which  way  the  light  moves.  Move  still 
closer  to  the  eye  and  observe  that  the  light  now  moves  with  the  rota- 
tion of  the  mirror.  It  is  to  be  remembered  that  the  myopic  eye  con- 
verges the  rays  leaving  it.  The  point  in  space  at  which  they  intersect 
is  the  point  of  reversal.  Obviously,  distally  to  this  point  the  light  must 
move  against,  and  inside  this  point,  with  the  rotation  of  the  mirror. 
Hence,  skiascopy  is  simply  an  accurate  method  of  determining  this 
point  of  reversal.     Draw  a  diagram  illustrating  the  reflection  in  myopia. 

Render  the  artificial  eye  hypermetropic  by  bringing  its  halves  closer 
together.  Place  your  eye  at  a  distance  of  1  m.  from  the  artificial  eye. 
Move  back  and  forth  and  note  that  the  movement  of  the  pupillary  light 
is  with  the  rotation  of  the  mirror,  no  matter  what  position  you  occupy. 
This  is  due  to  the  fact  that  the  hypermetropic  eye  does  not  form  a 


THE    SENSE    OROANS  197 

point  of  reversal  because  it  emits  divergent  rays.  Now  interpose  a 
convex  lens  in  front  of  the  artificial  ejx',  therein'  converging  these  rays 
and  producing  an  artificial  point  of  reversal  and,  so  to  speak,  an  artificial 
myopia.  This  lens  accomplishes  two  things,  namely,  it  neutralizes  the 
divergence  of  the  rays,  and  secondly,  converges  them  sufficienfly  to  inter- 
sect. In  order  to  ol)tain  the  degree  of  hypermetropia  existing  in  this 
eye,  determine  the  point  of  reversal  as  in  normal  myopia.  Sul)tract 
the  degree  of  myopia  from  the  total  strength  of  the  lens.  The  remainder 
of  the  focal  strength  of  the  lens  is  the  strength  whicii  is  requiicd  to  over- 
come the  hypeYmetropia.  Draw  a  diagram  showing  the  reflection  in  the 
hypermetropic  eye. 

Select  a  number  of  students  who  are  either  near-sighted  or  far- 
sighted  and  determine  the  degree  of  ametropia  in  each.  For  example, 
if  the  erect  movement  is  obtained  as  close  as  55  cm.  from  the  eye  and 
the  reversal  as  near  as  80  cm.,  the  point  of  reversal  lies  at  a  distance 
of  about  67  cm.  The  myopia  equals  1.50  D.  Again,  supposing  that 
the  movement  of  the  hght  in  the  pupil  is  found  to  be  with  the  mirror  at 
all  distances,  then  interpose  a  5  D.  (convex)  lens.  If  the  point  of  re- 
versal is  now  at  a  distance  of  1  m.,  4  D.  have  been  used  to  neutralize 
the  divergency  and  1  D.  to  render  the  rays  convergent.  Consequently, 
the  degree  of  hypermetropia  equals  4  D. 


LESSON  XLII 

THE  SENSE  ORGANS  (Concluded) 

VISION 

1.  The  Blind  Spot. — Make  a  small  cross  mark  upon  a  white  strip  of 
paper.  AboUt  8  cm.  to  the  right  of  it  make  a  black  dot  of  the  size  of 
a  large  pea.  Close  your  left  eye  and  with  your  right  eye  gaze  fixedl\' 
at  the  cross  lines,  allowing  the  dot  to  he  in  the  outer  visual  fi(>ld.  Bring 
the  card  closer  to  the  eye  until  the  dot  disappears  completely.  Move 
the  card  still  closer;  the  dot  reappears.  Draw  a  diagram  explaining 
this  defect  in  the  visual  held.  What  position  does  the  yellow  spot 
occupy  in  relation  to  the  bhnd  spot,  antl  how  is  this  disturbance  over- 
come in  binocular  vision. 

With  yoin-  right  eye  gaze  at  an  object  placed  at  a  distance  of  6  m. 
from  you.  Adjust  the  position  of  a  fellow  student  in  such  a  way  that 
his  head  disappears  conipletel}'. 

Make  a  small  cross  upon  a  white  strip  of  paper.  On  each  side  of  it 
and  about  4  cm.  from  it  make  two  black  dots.  Hold  your  left  hand 
with  its  inner  margin  against  the  bridge  of  your  nose.  With  your  right 
hand  hold  the  above  figure  in  front  of  your  eyes,  and  while  steadily 
fixing  the  cross  move  the  paper  to  and  fro  until  you  reach  the  cUstance 
at  which  both  dots  disappear. 

2.  The  Contours  of  the  Blind  Spot. — Place  the  chin  of  the  subject 
upon  a  support  and  adjust  a  slun^t  of  white  paper  about  50  cm.  vertically 
in  front  of  him.  Ask  him  to  gaze  with  his  right  eye  at  a  small  black 
dot  upon  the  paper.  Fasten  a  pin  with  a  large  black  head  upon  a  straw, 
and  move  this  pin  from  without  inward  along  the  horizontal  meridian 
of  the  eye.  Indicate  upon  the  paper  the  moments  when  the  head  of  the 
pin  disappears  and  reappears.  Draw  a  vertical  line  about  midway  be- 
tween these  two  points  and  also  several  obUque  hnes.  Indicate  upon 
all  these  lines  the  moments  when  the  pin  disappears  and  reappears. 
Connect  these  points  to  obtain  a  continuous  line.  Note  that  the  field 
is  irregularly  oval  in  its  outline,  owing  to  the  fact  that  the  blood-vessels 
emerging  from  the  optic  disk  are  also  insensitive  to  the  light  rays. 

3.  The  Yellow  Spot. — Having  rested  the  eye  for  a  minute  or  two, 
look  through  a  fiat  bottle  containing  a  fairly  strong  solution  of  chrome 
alum.  It  is  best  to  hold  the  bottle  against  a  sheet  of  white  paper. 
Since  the  pigment  of  the  j'cllow  spot  absorbs  the  blue  and  green  rays 
and  transmits  the  others,  the  predominant  tinge  imparted  to  the  area 
corresponding  to  the  macula  lutea  will  be  red  (purple). 

4.  The  Retinal  Blood-vessels. — While  the  subject  turns  his  eyes 
laterally  upon  a  dark  wall,  concentrate  a  beam  of  light  from  the  optical 
lantern  upon  the  exposed  sclerotic  coat  directly  behind  the  region  of 

199 


200         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

the  ciliary  body.  Give  the  lens  used  to  concentrate  the  light  a  gentle 
rocking  motion.  The  visual  field  will  then  appear  to  the  subject  as 
reddish  3'ellow,  through  which  dark  figures  are  passing.  The  latter 
assume  the  character  of  a  network,  in  agreement  with  the  branching 
blood-vessels  (Purkinje's  figures).  Bj^  this  means  shadows  of  the 
blood-vessels  are  cast  upon  regions  of  the  retina  not  ordinarity  exposed 
to  them.  It  is  essential,  however,  that  these  shadows  move,  because 
the  retina  quickl}-  adapts  itself  to  continued  stimulation. 

Make  a  pinhole  in  a  card  and  hold  it  directly  in  front  of  one  e3'e,  the 
other  being  closed.  Direct  the  visual  axis  upon  a  bright  and  evenly 
illuminated  sheet  of  white  paper  placed  in  front  of  a  lamp.  Move  the 
card  from  side  to  side.  Vertically  running  figures  will  be  apparent. 
Move  the  card  up  and  down.     Horizontal  vessels  will  now  be  in  evidence. 

Gaze  at  a  white  cloud  through  a  thick  piece  of  blue  glass.  Many 
bright  points  followed  by  shadows  will  be  seen  to  traverse  the  visual 
field  in  a  constant  procession.  The  latter,  in  all  probability,  represent 
the  red  blood-corpuscles. 

5.  Direct  and  Indirect  Vision. — Draw  a  figure  upon  a  white  sheet 
of  paper,  consisting  of  one  central  dot  surrounded  by  six  others  at  a 
slight  distance  from  it.  With  your  right  eye  fixate  a  small  object  at 
a  distance  of  50  cm.  from  you.  Bring  the  aforesaid  figure  slowly  into 
the  line  of  vision.  Note  that  the  individual  dots  coalesce  at  some 
distance  from  the  latter.  They  are  severally  in  evidence  only  when  the 
figure  is  brought  into  the  visual  line.  Obviously,  at  this  time,  the  rays 
of  fight  emitted  by  the  figure  are  focalized  in  the  fovea,  i.  e.,  in  the 
region  of  the  greatest  acuity  of  vision.  When',<made  to  fall  upon  out- 
l}dng  districts  of  the  retina  the  rays  cannot  form  a  precise  image. 

Gaze  at  an  object  in  a  brightly  illuminated  room.  Note  that  the 
object  is  unconsciously  brought  into  direct  line  with  the  fovea.  Darken 
the  room.  Note  that  at  first  your  vision  is  very  poor,  but  gradually 
adapts  itself  to  the  low  intensity  of  light.  Also  observe  that  you  now 
endeavor  to  focalize  objects  by  bringing  them  upon  the  outer  zones  of 
the  retinae. 

Focalize  a  single  word  upon  a  page  of  print.  Note  that  only  the 
word  looked  at  is  perfectly  clear,  while  those  farther  away  from  it  in 
any  direction  are  not  clear. 

Draw  radiate  lines  upon  the  blackboard  and  equip  each  with  cross 
marks  at  distances  of  5  degrees  from  one  another.  Fix  any  one  of  the 
cross  marks  and  note  that  the  others  are  at  this  time  not  perfectly  clear. 

6.  Associated  Movements  of  the  Eyes. — Close  one  eye  and  place 
the  tip  of  your  index-finger  upon  the  upper  eyelid.  Note  that  the  focal- 
izing of  an  object  with  the  other  eye  invariably  produces  a  co-ordinated 
movement  in  the  closed  eye. 

7.  Positive  After-images. — Having  rested  the  eyes  for  a  short  time, 
look  suddenly  at  a  lighted  incandescent  lamp  and  shut  the  eyes  again 
after  a  distinct  image  of  the  lamp  has  been  formed.  Note  the  after- 
effect. 


THE    SENSE    OUOANS 


201 


Close  tho  pyos  for  a  fow  seconds.  Look  at  a  fias  flame  in  which  some 
common  salt  is  burninji;,  and  then  at  a  sheet  of  white  paper.  Does  the 
after-image  move  with  the  eye? 

Obtain  an  after-image  by  suddenly  turning  off  the  gas  in  a  dark  room, 
or  by  gazing  at  a  window  for  half  a  second  and  then  closing  the  eyes. 

8.  Negative  After-images.-  Having  rested  the  eyes,  gaze  for  about 
half  a  minute  at  a  small  white  square  on  a  black  background.  Suddenly 
place  a  sheet  of  white  paper  over  the  black.  How  does  the  present 
after-image  differ  from  those  obtained  previously. 

Look  at  a'black  sciuare  on  a  white  ground;  then  suddenly  let  the 
eyes  rest  upon  a  gray  screen.  Observe  the  after-image,  and  note  the 
apparent  increase  in  its  size  when  the  gray  screen  is  moved  farther 
away  from  the  eye. 

Gaze  at  a  bright  red  square  upon  a  black  ground;  then  look  at  a 
white  surface.     Does  the  bluish-green  after-image  show  periodic  varia- 


FiG.  115. — Rothe's  Rotatory  Apparatus  for  Color  Disks.    It  is  so  Arranged  as  to 
Give  Various  Rates  of  Rot.\tion  by  Combi.nixg  the  Motions  of  1,  2,  and  3. 

tions?     Repeat  the  experiment  with  a  green  square.     Note  that  the 
color  of  the  after-image  is  complementary  to  that  of  the  square. 

Place  the  red  and  green  squares  side  by  side  on  the  black  surface. 
Look  at  them  steadily  for  about  twenty  seconds,  and  then  slip  a  sheet 
of  white  paper  over  the  whole. 

9.  Fusion  of  Gray  and  White. — By  means  of  jMaxwell's  color  mixer 
rotate  the  black  and  white  disk  supplied  for  this  experiment  until  you 
have  obtained  complete  fusion  of  the  black  and  white  in  the  outer  zones 
of  the  disk. 

Increase  the  frequency  of  the  revolutions  of  the  disk  until  even  the 
central  zones  appear  of  a  uniform  gray  color.  Darken  the  room  some- 
what, and  determine  how  many  revolutions  are  necessary  to  produce 
a  gray  of  the  same  quality  as  before. 

10.  Fusion  of  Colors. — Rotate  two  large  disks,  colored  respectively 
red  and  green,  and  adjust  the  colored  areas  so  as  to  obtain  a  dark  yel- 


202  ADVANXED    LESSONS    IX    PRACTICAL    PHYSIOLOGY 

low.  Match  this  color  by  inserting  two  small  disks,  black  and  j-ellow 
respectively.  Obtain  a  blue  color  by  means  of  two  large  disks  colored 
green  and  j'ellow.  ]\Iatch  the  blue  color  by  means  of  two  small  disks, 
respectively  blue  and  black. 

Use  three  disks  colored  red,  green,  and  violet.  The  wave-lengths  of 
these  colors  should  correspond  as  closely  as  possible  to  those  of  the 
corresponding  colors  of  the  solar  spectrum.  Arrange  the  colored  areas 
in  the  proportion  of  red,  118  degrees;  green,  146  degrees;  and  violet, 
96  degrees.  Rotate  the  disks  until  you  have  obtained  a  gray  color. 
IMatch  this  gra}"  b}"  means  of  two  small  disks,  colored  black  and 
white. 

11.  Complementary  Colors. — Select  from  the  series  of  colored  disks 
provided  for  this  experiment  one  of  a  blue  color.  Determine  what 
color,  when  mixed  with  this  blue  in  definite  proportion,  w^ill  turn  it 
gray  or  nearl}^  white.  The  color-mixer  should  make  from  40  to  50 
revolutions  in  a  minute.  If  the  gray  remain  slighth'  tinged  with  color, 
add  a  small  section  of  a  third  color  disk,  neutrahzing  with  green  if  the 
tinge  inclines  toward  red,  and  with  red  if  the  tinge  exhibits  a  greenish 
hue.  Determine  in  the  same  manner  the  colors  complementary  to  red, 
yellow,  orange,  and  green. 

12.  Intensity  of  Light  and  Quality  of  Color  (Purkinje's  Phenom- 
enon).— Take  two  small  squares  of  red  and  blue  paper  respectively, 
which  in  a  moderate^  bright  Hght  possess  nearlj^  the  same  intensity 
of  color.  Observe  them  again  in  a  partially  darkened  room.  "Which 
color  appears  to  be  the  brighter? 

13.  Color-blindness. — Place  Holmgren's  worsteds  upon  a  weU  hghted 
sheet  of  white  paper.  Employ  as  a  test  color  hght  green,  i.  e.,  a  mixture 
of  white  and  pure  green,  and  ask  the  subject  to  select  from  a  lot  of  skeins 
all  those  which  appear  to  him  to  be  of  this  hght  green  color.  If  he 
choose  one  or  more  "confusion-colors" — in  this  case  pink  or  yellow — 
he  should  be  given  a  skein  of  a  pale  rose  color,  and  be  asked  to  pick  out 
all  the  skeins  which  he  thinks  would  match  it.  If  the  subject  be  red- 
blind,  he  will  select  blue  and  \dolet;  if  green-blind,  gra}'  and  green. 

Ask  the  subject  to  match  a  bright  red  skein.  If  red-bhnd,  he  will 
choose  green  and  brown;  if  green-blind,  red  and  light  brown. 

14.  Contrast.— Of  two  equally  large  strips  of  gra}^  paper,  place  one 
upon  a  sheet  of  white  paper,  and  the  other  upon  a  sheet  of  black.  Wliich 
strip  appears  to  be  the  brighter  ? 

Place  these  sheets  close  together,  each  sheet  bearing  its  gray  slip. 
Gaze  at  both  slips  for  twenty  seconds,  and  then  shut  the  eyes.  Which 
after-image  seems  the  brighter? 

Place  a  cross  of  gray  paper  in  the  middle  of  a  large  sheet  of  green 
paper  and  cover  both  cross  and  background  with  tissue  paper.  Note 
the  color  now  imparted  by  the  cross.  Place  the  gray  cross  upon  a  red 
background  instead  of  a  green.  Cover  the  whole  with  tissue  paper  as 
before  and  note  the  color  of  the  cross. 

Place  a  strip  of  gray  paper  across  the  junction  of  a  red  and  a  green 


THE    SENSE    ORGANS  203 

sheet  of  paper  and  covct  the  whole  with  tissue  paper.  Note  the  ap- 
parent color  of  the  strip. 

15.  Irradiation. — Place  a  circular  piece  of  black  paper  1  cm.  in 
diameter  upon  a  white  circle  of  paper  2  cm.  in  diameter,  and  a  white 
circle  1  cm.  in  diameter  upon  a  black  circle  2  cm.  in  diameter  Hold 
the  circles  at  some  distance  from  the  eyes  and  note  their  apparent  size. 

Divide  a  square  into  four  small  stjuares  of  equal  size,  and  blacken  the 
left  upper  ancl  the  right  lower  of  these  four  fields.  Observe  that  the 
white  scjuares  appear  to  be  larger  than  the  black. 

It).  Single  and  Double  Images. — Adjust  your  vision  so  as  to  see 
clearly  witii  both  eyes  a  vertical  rod  held  GO  cm.  in  front  of  them. 
Hold  upright  the  index-finger  of  one  hand  in  the  binocular  line  about 
35  cm.  from  the  eyes,  and  observe  the  double  image  of  the  finger. 
Close  the  right  eye  and  note  whether  the  right  or  the  left  image  dis- 
appears. Accommodate  for  the  finger,  and  observe  the  resulting  double 
image  of  the  rod.  Close  one  eye  and  note  which  image  disappears. 
Explain. 

Accommodate  for  an  object  placed  about  2  m.  in  front  of  the  eyes. 
Hold  a  pencil  upright  in  the  binocular  line  about  30  cm.  from  the  eyes. 
Move  the  pencil  slightly  toward  the  right  eye.  Observe  that  one  image 
disappears  when  the  images  he  asymmetrically  to  one  side  of  the  Une 
of  vision  only,  the  image  in  the  right  eye  being  perceptible  in  the 
present  case.  Close  the  right  eye  and  in  this  way  render  the  second 
image  perceptible. 

17.  Binocular  Fusion  of  Dissimilar  Images. — Fasten  a  red  and  a 
green  postage  stamp  upon  a  piece  of  cardboard  at  a  distance  equaling 
the  interocular  distance.  Observe  them  in  the  stereoscope  and  note 
that  their  images  are  fused  into  a  single  one. 

18.  Relation  of  Binocular  Vision  to  Judgments  of  Direction. — Draw 
a  sheet  of  paper,  with  a  pinhole  in  it,  horizontally  past  the  eyes,  starting 
well  to  the  right  of  the  eye.  To  what  plane  of  the  head  are  the  two 
successive  images  referred? 

19.  Relation  of  Binocular  Vision  to  Judgments  of  Solidity. — Ex- 
amine a  series  of  pictures  in  the  stereoscope.  Draw  a  diagram  to  show 
the  manner  in  which  judgments  of  solidity  are  formed. 

20.  Relation  of  Binocular  Vision  to  Judgment  of  Distance. — Close 
one  eye  and  hold  the  index-finger  of  the  left  hand  vertically  in  front 
of  the  other  eye.  Try  to  strike  the  left  index-finger  with  the  index- 
finger  of  the  right  hand. 

Close  one  eye  and  try  to  dip  the  index-finger  of  one  hand  into  the 
mouth  of  a  bottle  held  about  25  cm.  in  front  of  the  other  eye. 

With  the  left  hand  hold  a  pencil  vertically  about  25  cm.  in  front  of 
the  eyes.  Gaze  at  the  pencil  for  a  few  seconds,  close  the  left  e\'e;  then 
cover  the  lower  part  of  the  pencil  with  your  right  index-finger  held 
vertically  between  the  object  and  the  eyes.  Try  to  strike  the  pencil 
with  the  finger. 

21.  Influence  of  Convergence  of  the  Visual  Axes. — Gaze  at   an 


204 


ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 


object  through  two  blackened  tubes  of  paper.  Cause  the  tubes  to 
converge  slowly  and  observe  the  apparent  increase  in  the  size  of  the 
object. 


^^ 


\ 


\ 


// 
// 


\ 
\ 


\ 

\  A 

\ 
\ 


\x 


\ 


/ 

■/ 


/ 


\\ 


\ 

\ 


\ 


Fig.  116. — Zollner's  Lines. 


22.  Optical  Illusions. — Examine  a  series  of  figures,  such  as  the  fol- 
lowing, and  give  reasons  for  the  illusion: 


A 


D  E 

Fig.  117. — To  Illustrate  the  Illusion  of  Subdivided  Space. 

(a)  Make  two  lines  parallel  and  draw  short  oblique  lines  through 
them.  Note  that  the  lines  now  slope  in  accordance  with  the  direction 
of  the  oblique  lines  (Fig.  116). 

(6)  Make  three  black  dots  {A,  B,  and  C)  at  equal  distances  from 


THE    SENSE   ORGANS  205 

one  another.     Between  .1  and  li  make  several  dots  of  equal  size.     .1 
and  B  will  then  appear  fartluM-  apart  than  li  and  C  (Fig.  117). 

(c)  Draw  two  horizontal  lines  of  equal  length  and  parallel  to  one 
another.     Upon  the  ends  of  one  draw  oblique  lines  outward  and  upon 


Fig.  lis. — Muller-Lter  Figures  to  Show  Illusion  in  Space  Perception.    The  Lines 

A   AND  B    ARE  of  THE  SaME  LeNGTH. 

the  ends  of  the  other  similar  lines  turned  inward.     The  latter  will  then 
appear  to  be  shorter  than  the  former. 

(d)  Draw  two  lines  of  equal  length  parallel  to  one  another.     Next 
to  this  figure  draw  another  of  the  same  dimensions  with  several  inter- 


FiG.   119. — To  Illustrate  the  Overestimation  of  Vertical  Lines. 

coursing  lines.     Note  that  the  second  figure  appears  to  be  larger  than 
the  first  (Fig.  117). 

(e)  Place  a  vertical  line  beside  a  horizontal  line  of  the  same  length. 
The  former  appears  to  be  the  longer  (Fig.  119). 


LESSOX  XLIII 

DIGESTION 

DEGLUTITION 

1.  Isolation  of  the  Esophagus. — Anesthetize  a  mammal  and  main- 
tain the  anesthesia  throuf^liout  the  following  experiments:  Perform 
tracheotom\'  low  down.  Separate  the  trachea  from  the  esophagus,  and 
excise  the  piece  of  trachea  situated  between  the  cricoid  cartilage  and 
the  metal  cannula.  Palpate  the  esophagus,  noting  its  texture  and 
movability. 

Expose  both  vagi  nerves  and  place  them  in  loose  ligatures.  In 
addition,  expose  their  superior  laryngeal  branches  and  place  them  in 
loose  ligatures. 

Make  a  median  incision  through  the  linea  alba.  Follow  the  an- 
terior wall  of  the  stomach  until  the  esophageal  gastric  junction  has 
been  reached.  Insert  a  straight  cannula  in  the  orifice  of  the  esophagus, 
and  connect  it  with  a  manometer  containing  water.  Cover  the  ab- 
dominal wound  with  a  cloth  moistened  with  warm  sahne  solution. 

2.  Wave  of  Deglutition.^ — Open  the  mouth  of  the  animal  and  touch 
the  fauces  with  a  moistened  plug  of  cotton.  Observe  the  swallowing 
movements  evoked  thereby.  Note  that  they  begin  in  the  mouth  and 
travel  downward  in  the  form  of  a  peristaltic  wave,  involving  the  different 
segments  of  this  passage  consecutively. 

Observe  the  displacement  of  the  column  of  water,  and  determine 
approximately'  the  interval  of  time  between  the  beginning  of  this  act 
and  the  moment  when  the  wave  has  reached  the  level  of  the  larj'nx, 
and  again  when  it  has  arrived  at  the  cardiac  end  of  the  stomach.  In 
which  segment  is  its  progress  slowest? 

Evoke  these  movements  by  stimulating  the  central  end  of  the 
superior  laryngeal  nerv(\ 

3.  Division  of  Esophagus.— Cut  transversely  across  the  cervical 
portion  of  the  esophagus.  Stimulate  the  central  end  of  the  superior 
laiyngeal  nerve,  evoking  peristalsis.  Does  the  wave  proceed  as  before, 
or  is  it  l)lockcd  at  the  line  of  the  section?     Explain. 

Raise  the  orifice  of  the  lower  segment  slightly.  Insert  an  elliptic 
piece  of  smooth  wood  secured  by  means  of  a  thread.  Does  the  intro- 
duction of  this  body  lead  to  a  wave  of  deglutition  in  this  segment? 
If  not,  excite  a  wave  in  the  normal  way,  either  by  stimulating  the 
superior  laryngeal  nerve  or  by  stimulating  the  mucous  membrane  of 
the  mouth.     Is  the  wood  now  jiropelled  onward?     Explain. 

4.  Influence  of  the  Vagi  Nerves.^Divide  the  right  vagus  nerve. 
Excite  deglutition  b}'  stimulation  of  the  superior  larj'ngeal  nerve.  Study 
the  character  of  the  wave.     Divide  the  left  vagus  nerve  and  repeat  this 

207 


208         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

stimulation.  What  differences  do  you  observe?  What  part  do  the 
vagi  nerves  play  in  deglutition  ?  Kill  the  animal  bj^  an  overdose  of 
ether.  Open  the  thorax  and  trace  the  esophagus  through  the  chest. 
Measure  its  total  length,  and  determine  the  velocity  of  the  wave  of 
deglutition. 

5.  Deglutition  in  the  Human  Subject. — Let  the  subject  take  a 
swallow  of  water  while  you  auscultate  first  over  the  region  of  the  larynx 
and  again  over  the  cardiac  orifice  of  the  esophagus.  Describe  the 
character  of  the  noises  heard.  Determine  the  approximate  interval 
between  them.  Chew  a  piece  of  bread  and  swallow  in  the  usual  way. 
Determine  the  interval  between  the  aforesaid  noises.  The  time  of 
deglutition  is  much  longer  in  the  latter  instance. 

6.  Percussion  of  the  Human  Stomach. — Let  the  subject  take  sodium 
bicarbonate  in  conjunction  with  tartaric  acid  and  assume  the  horizontal 
position.  Percuss  the  region  of  the  stomach,  outlining  this  organ  with 
colored  chalk.  Determine  the  position  of  the  pyloric  orifice.  What 
relation  does  the  lower  boundary  of  the  stomach  bear  to  the  umbilicus? 
Where  would  this  boundary  be  found  in  a  dilated  organ?  Explain  the 
fact  that  gas  is  not  erupted  until  the  subject  assumes  the  recumbent 
position. 


LESSON  XLIV 

DIGESTION  (Continued) 
SECRETION  OF  SALIVA 

1.  Isolation  of  the  Secretory  Nerves. — Anesthetize  a  mammal  and 
maintain  the  anesthesia  throufiiiout  the  following  experiments  until  the 
animal  has  been  killed.  Perform  traeheotomy.  Expose  the  left  com- 
mon carotid  artery  and  insert  in  its  central  end  a  straight  cannula.  On 
the  opposite  side  make  a  longitudinal  cut  through  the  skin  a  little  to 
one  side  of  the  median  line,  and  l^eginning  at  a  point  opposite  the  canine 
teeth.  Prolong  it  backward  to  the  angle  of  the  jaw.  Cut  through  the 
platysma  myoides.  The  next  laj^er  of  muscle-fibers  is  arranged  trans- 
versely. Carefully  split  this  layer  (muse,  mylohyoideus)  with  forceps, 
reflecting  its  halves  to  the  right  and  left.  Let  the  assistant  place  his 
index-finger  upon  the  floor  of  the  mouth  and  pull  it  away  from  the  side 
of  the  lower  jaw.     Identify  the  lingual  nerve  which  passes  transversely 


Fig.  120. — Schema  Illustrating  the  Nerve  Supply  of  the  Submaxillary  Gl.\nd. 
SG,  Submaxillary  filaiid;  supplied  by  a  small  artery  from  the  carotid  sy.stem  (CA). 
It  is  drained  l)y  a  small  vein  which  generally  enters  the  facial  (FV)  at  its  point  of  con- 
fluence with  the  lingual  vein  (LV).  The  external  {ES\^  and  internal  (JSl")  maxillary 
veins  invest  the  gland  and  unite  to  form  the  external  jugular  vein  (EJV).  The  sympa- 
thetic nerve  supply  is  derived  from  the  sup.  cerv.  ganglion  (SC'G).  The  chorda  tynipani 
{CT)  attaches  itself  to  the  lingual  nerve  L.V  and  then  to  Wharton's  duct  (W);  S,  lower 
jaw. 

across  the  floor  of  the  mouth  at  about  the  junction  of  the  middle  and 
posterior  thirds  of  the  jaw.  Follow  the  latter  in  a  central  direction  until 
you  reach  the  chorda  tympani  nervT  and  the  duct  of  the  submaxillary 
gland  (Wharton's).  Isolate  the  chorda  tympani  nerve  at  the  point 
where  it  leaves  the  lingual  nerve,  and  place  it  in  shielded  electrodes. 
Ligate  the  duct  of  the  submaxillary  gland  and  stimulate  the  chorda 
tympani  for  a  few  seconds,  so  as  to  distend  the  duct  with  saliva.  Insert 
a  cannula.  Exi:)Ose  the  vagosj'mpathetic  nerve  of  the  same  side,  cut 
it,  and  arrange  for  stimulating  its  central  end  (toward  the  head)  with  a 
weak  tetanizing  current. 

14  209 


210         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

2.  Function  of  the  Chorda  Tympani  Nerve  .^Stimulate  the  chorda 
tympani  for  fifteen  seconds  and  count  the  number  of  drops  of  sahva  which 
escape  during  this  time.  Observe  the  degree  of  viscosity  of  the  sahva. 
Pour  it  from  one  beaker  into  another,  noting  its  viscidity.  Repeat  this 
test. 

3.  Function  of  the  Sympathetic  Nerve. — Stimulate  the  central  end 
of  the  sympathetic  nerve  and  count  the  number  of  drops  of  saliva.  Ob- 
serve its  viscosity  and  viscidity.     Contrast  it  with  the  chorda  saliva. 

4.  Secretory  Pressure. — Record  on  the  kymograph  the  blood- 
pressure  prevaihng  in  the  carotid  artery  of  this  animal.  Disconnect 
the  carotid  artery  from  the  manometer  and  connect  the  latter  with  the 
duct  of  the  submaxillary  gland.  Stimulate  the  chorda  tympani  for  a 
considerable  time,  with  occasional  intervals  of  rest,  and  record  the 
pressure  under  which  secretion  still  takes  place.  Allow  the  drum  to 
revolve  very  slowly.  The  pressure  in  the  salivary  duct  may  be  raised 
a  considerable  distance  above  the  general  blood-pressure,  proving  thereby 
that  filtration  is  not  the  only  factor  concerned  in  the  formation  of  this 
secretion.     Enumerate  the  other  factors. 

5.  The  Vasomotor  Changes  in  the  Submaxillary  Gland  Produced  by 
Stimulation  of  the  Chorda  Tympani  and  Sympathetic  Nerve. — Reflect 
the  skin  and  expose  the  large  veins  in  the  vicinity  of  the  submaxillary 
gland.  Ligate  the  internal  maxillary  and  facial  veins  opposite  the 
anterior  end  of  the  gland,  and  ligate  the  sublingual  vein  about  2  cm. 
distally  to  its  junction  with  the  facial  vein.  Carefully  destroy  by  tor- 
sion the  larger  cutaneous  veins  which  empty  their  contents  into  the 
aforesaid  veins  centrally  to  the  ligatures.  The  vein  which  returns  the 
blood  from  the  submaxillary  gland  pursues  a  very  irregular  course.  In 
most  cases,  however,  it  joins  one  or  the  other  of  the  above-mentioned 
veins  at  a  point  nearer  to  the  heart  than  where  the  ligatures  have  been 
applied.  If  this  relationship  prevails  in  the  mammal  used  for  this 
experiment,  only  the  blood  returned  from  the  submaxillary  gland  will 
be  able  to  enter  the  external  jugular  vein. 

Insert  a  cannula  in  the  distal  end  of  the  external  jugular  vein  near 
the  point  where  the  internal  and  external  maxillary  veins  unite.  Con- 
nect the  cannula  with  a  bottle  having  an  inlet  and  an  outlet  tube,  and 
containing  a  solution  of  magnesium  sulphate.  When  the  blood  is  al- 
lowed to  flow  into  the  bottle  it  will  displace  an  equal  quantity  of  this 
solution,  which  can  be  measured  in  a  graduated  cylinder. 

Measure  the  blood  flow  for  a  short  time,  then  stimulate  the  chorda 
tympani  nerve  until  you  have  obtained  a  decided  increase  in  the  blood 
flow.  Allow  this  flow  to  become  normal  again.  Stimulate  the  sympa- 
thetic nerve  until  the  blood  flow  has  been  considerably  lessened.  These 
results  are  referable  to  the  fact  that  the  chorda  possesses  vasodilator 
qualities,  whereas  the  sympathetic  is  a  vasoconstrictor  nerve. 

6.  Secretion  by  the  Bloodless  Gland. — Render. the  submaxiUary 
gland  bloodless  by  ligating  the  blood-vessels  supplying  the  head,  or  by 
decapitating  the  animal.     Stimulate  the  chorda  tympani,  and  measure 


DIGESTION  211 

the  quantity  of  saliva  secreted.  How  lonp;  after  the  cessation  of  the 
blood  flow  may  saliva  be  obtained?  What  conclusion  seems  justified 
rep;ardinp;  the  secretory  activity  of  the  cells  of  this  p;land? 

7.  Dissection  of  the  Salivary  Glands. — Isolate  the  subliii<i;uul  and 
parotid  j^huuls  and  (licir  excretory  ducts. 

Examine  preparations  of  resting  and  active  tissue  from  the  parotid 
or  submaxillar}'  gland  under  the  microscope. 


LESSON  XLV 
DIGESTION  fContinued) 

SECRETION  OF  PANCREATIC  JUICE.     ACTION  OF  SECRETIN. 

ENTEROSTOMY 


GASTRO- 


1.  Preparation  of  Secretin. — Anesthetize  a  mammal  and  maintain 
the  anesthesia  tiiroui^hout  the  following  experiments:  Perform  trac-he- 
otomy.  Open  the  abdomen  by  an  incision  throufj;h  the  linea  allm. 
Identify  the  pyloric  sphincter.  Beginning  at  this  point  isolate  a 
segment  of  intestine  about  1  m.  in  length.  Remove  it;  slit  its  wall, 
and  wa.sh  it  thoroughly  in  running  water.  Kill  the  animal  b}'  an 
overdose  of  ether.  Scrape  oti'  the  mucous  lining  of  the  segment  of  in- 
testine just  removed  with  a  piece  of  glass,  and  immerse  this  material 
in  saline  solution  and  sand.  Add  to  it  three  or  four  times  its  volume  of 
0.4  per  cent.  HCl  and  place  it  in  the  ice-chest.     Shortly  before  being 


Fig.   121. — DiAiiR.\M  to  Show  the  Position  of  the  Ducts  of  the  Pancre.\s. 
D,  Duodenum;  P,  pancreas;  DC,  ductus  choledochus;  DW,  ductus  Wirsungianus;  DS, 

ductus  Santorini. 

used  add  KOH  to  this  decoction  of  the  duodenal  mucosa  until  changed 
to  an  alkaline  reaction.  Strain  through  muslin  and  filter.  As  much 
as  50  c.c.  of  this  preparation  should  be  used  at  a  time.  Since  the  acidi- 
fied decoction  may  be  kept  for  some  time,  it  is  advisable  for  economic 
reasons  to  prepare  it  from  some  of  the  animals  used  during  one  of  the 
exercises  immediately  preceding.  If  an  animal  has  been  used  especially 
for  obtaining  secretin,  it  should  be  kept  until  the  end  of  this  exercise 
for  purposes  of  dissection. 

2.  Collection  of  Pancreatic  Juice. — Anesthetize  a  mammal  and  main- 
tain the  anesthesia  throughout  the  following  experiments:  Perform 
tracheotomy.     Open  the  abdominal  cavity  by  an  incision  in  the  linea 

213 


214  ADVANCED    LESSONS   IN    PRACTICAL   PHYSIOLOGY 

alba.  Identify  the  pyloric  sphincter  and  duodenum.  Note  the  posi- 
tion, shape,  color,  etc.,  of  the  pancreas.  Inspect  the  body  of  this  organ. 
Note  how  closely  it  invests  the  duodenum.  Identify  the  duct  of  Wir- 
sung.  Open  the  duodenum  in  this  region  and  locate  the  papilla  through 
which  the  pancreatic  and  common  bile-ducts  discharge  their  contents. 
Insert  a  straight  glass  cannula  in  this  orifice,  and  place  a  chp  upon  the 
common  duct  farther  distally. 

Adjust  the  mouth  of  the  cannula  so  that  the  drops  of  pancreatic 
secretion  may  fall  upon  the  spoon  of  a  receiving  tambour.  By  means 
of  narrow  rubber  tubing  connect  this  tambour  with  a  recording  drum 
registering  the  number  of  drops  upon  the  paper  of  a  slowly  revolving 
kj^mograph.     Add  a  time-curve. 

3.  Action  of  Secretin. — Expose  the  right  external  jugular  vein  and 
insert  a  cannula  in  its  central  end  (see  Lesson  X).  Slowly  inject  50  c.c. 
of  the  activated  preparation  of  duodenal  mucosa.  Register  the  drops 
of  pancreatic  juice  in  the  manner  just  described.  Compare  the  results. 
Disconnect  the  apparatus. 

4.  Gastro-enterostomy. — Procure  curved  needles,  catgut,  and  oper- 
ating instruments.  Select  a  segment  from  the  upper  portion  of  the 
jejimimi.  Bring  its  flat  surface  against  the  region  of  the  greater  curva- 
ture of  the  stomach,  avoiding  the  blood-vessels  of  this  region.  Approxi- 
mate these  surfaces,  being  careful  to  give  a  normal  curvature  to  the 
duodenum.  Make  an  incision  about  6  cm.  in  length  in  the  anterior 
wall  of  the  stomach  at  a  safe  distance  from  the  blood-vessels  passing 
along  the  greater  curvature.  Make  a  similar  incision  in  the  convex 
side  of  the  loop  of  the  jejunum.  Suture  the  two  orifices  in  apposition, 
first  by  an  external  serous  suture  carried  along  one  side  of  the  orifice 
and  then  by  an  internal  row  of  sutures  embracing  the  mucosa.  Repeat 
on  the  other  side  in  the  reverse  direction.  What  is  the  purpose  Of  this 
operation?  Discuss  physiologic  points  for  and  against  this  operation. 
Under  what  circumstances  may  it  produce  beneficial  results?  Kill  the 
animal  by  an  overdose  of  ether. 


L1-:SS()\  XLVI 

DIGESTION  (Concluded) 

LACTEALS  AND  THORACIC  DUCT.     PERISTALSIS.     SECRETION  OF  BILE 

1.  Lacteals. — Anosthctizo  a  cat  which  lias  boon  feci  with  fatty  food 
several  hours  beforehand,  and  maintain  the  anesthesia  throughout  the 
following  experiments:  Perform  tracheotomy.  Open  the  abdomen  by 
a  longitudinal  cut  in  the  median  line,  and  thus  expose  the  viscera. 
Throughout  the  subsequent  experinu^nts  keep  the  viscera  warm  by 
applying  cloths  moistened  with  warm  physiologic  salt  solution.  Ex- 
amine the  walls  of  the  intestine  and  the  mesentery.  Identify  the  lac- 
teals filled  with  chyl(\  and  note  their  ])eaded  appearance.  These  con- 
strictions indicate  the  positions  of  the  lymphatic  valves.  Trace  the 
lacteals  to  the  receptaculum  chyh,  the  enlarged  abdominal  end  of  the 
thoracic  duct,  which  lies  opposite  the  kidneys. 

2.  Peristalsis. — In  the  cat,  spontaneous  peristaltic  movements  of 
the  small  intestine  are  seldom  in  evidence.  Give  reasons  for  this 
motor  quiescence.  Stimulate  the  intestine  mechanically  and  elec- 
trically and  watch  the  resulting  contractions. 

Is  the  stomach  contracting?  Stimulate  its  surface  at  the  fundus 
and  at  the  pylorus.     Compare  the  results. 

Expose  the  right  vagus  nerve;  cut  it,  and  stinudate  its  distal  stump. 
Observe  the  movements  of  the  stomach  and  intestine.  What  is  their 
character? 

3.  Chyle. — Slit  open  a  distal  lacteal.  With  a  pipet  transfer  a  few 
drops  of  chyle  to  a  watch-glass  and  observe  the  coagulation.  Place  a 
drop  on  a  glass  slide  and  examine  it  microscopicall}',  identifying  white 
corpuscles  and  fat  globules.  Close  the  opening  in  the  lacteal  by  means 
of  an  artery  clamp. 

Expose  the  region  of  the  hepatic  artery  and  trace  the  numerous 
lymphatics  to  the  hilum  of  the  liver.  What  is  their  appearance?  What 
is  the  character  of  their  contents? 

4.  Secretion  of  Bile. — Ligate  the  common  bile-duct  just  above  its 
entrance  into  the  duodenum,  and  insert  a  cannula  in  its  hepatic  end. 
pjnpty  the  gall-bladder  by  gently  squeezing  it  between  your  fingers  and 
occlude  the  cystic  duct  by  means  of  an  artery  clamp.  Connect  the 
cannula  with  a  graduated  cyhnder.  Read  off  the  quantity  of  bile  so 
far  collected.  Note  the  effect  upon  its  level  of  the  respiratory  move- 
ments. Ascertain  by  Heading  the  amount  of  bile  that  is  secreted  in  a 
given  period  of  time.  After  fifteen  minutes  place  the  graduated  cyl- 
inder in  a  vertical  position,  and  determine  the  pressure  under  which  the 
bile  is  being  secreted.     What  is  the  relationship  between  the  secretory 

215 


216  ADVANCED    LESSONS    IN    PRACTICAL   PHYSIOLOGY 

pressure  and  the  blood-pressure  in  the  portal  vein?  Obviously,  the  bile- 
pressure  is  determined  in  this  ease  in  mm.  H2O.  Divide  by  13.5  in 
order  to  obtain  the  corresponding  value  in  mm.  Hg.  Since  the  portal 
pressure  in  cats  amounts  to  about  7  mm.  Hg  while  the  secretory  press- 
ure frequently  rises  to  15  mm.  Hg,  it  may  be  concluded  that  the  hepatic 
cells  are  capable  of  secreting  even  against  a  pressure  higher  than  that 
under  which  thej-  obtain  their  material. 

5.  Experimental  Jaundice.— Inject  into  the  bile-duct  a  saturated 
solution  of  indigo-carmin,  noting  by  a  watch  the  time  when  the  injec- 
tion has  been  begun.  Clamp  the  common  duct.  Watch  for  the  blue 
color  to  appear  in  the  skin,  the  mucous  membrane  of  the  mouth,  the 
conjunctiva,  and  the  chyle  in  the  lacteals.  Squeeze  the  urinary  bladder 
at  intervals  and  expel  a  small  quantity  of  urine.  How  soon  after  the 
beginning  of  the  injection  does  the  urine  assume  a  blue  color? 

6.  Thoracic  Duct. — Arrange  for  artificial  respiration.  Open  the 
chest  and  expose  the  thoracic  duct  on  the  left  side  of  the  spinal  column. 
It  is  now  rendered  clearly  visible  by  the  blue  chyle. 

7.  The  Stomach  Contents. ^ — Palpate  the  stomach.  Has  the  food 
been  fulh'  reduced  mechanically?  Evacuate  its  contents.  Wash  the 
gastric  mucosa  and  note  its  soft  velvety  texture.  Examine  preparations 
of  gastric  glands  under  the  low  and  high  powers  of  a  microscope.  Iden- 
tify the  chief  and  parietal  cells. 


LESSON  XLVII 
ABSORPTION 

OSMOSIS.      INTESTINAL    PERISTALSIS.    SECRETION    OF    INTESTINAL 
JUICE.     ABSORPTION  FROM  THE  SMALL  INTESTINE 

1.  Osmosis.^ — Prepare  an  osmometer  by  tying  a  piece  of  fish  condom 
or  other  semipennoahlo  membrane  over  the  orifice  of  a  thistle  tube. 
Fill  the  chamlxT  of  this  tube  with  a  concentrated  solution  of  mag- 
nesium sulphate.  Fill  a  beaker  with  distilled  water  and  suspend  .the 
filled  thistle  tube  in  the  water  so  that  the  levels  of  the  fluids  agree. 
Attach  a  narrow  glass  tube,  about  1  m.  in  length,  to  the  end  of  the 
thistle  tube,  and  allow  the  apparatus  to  stand  for  twenty-four  hours. 


iUli 


-m.^\o^' 


■  «i»  Jwj  - 


£:^:5rH.o=^?^Ez 


Fig.  122. — A  Simple  Osmometer. 
The  receptacle  contains  water,  and  the  cell  a  solution  of  magnesium  sulphate.     As 
the  molecules  of  water  are  drawn  through  the  semipernieahle  membrane  the  level  of  the 
MgS04  solution  rises. 

Already  in  the  course  of  an  hour  or  two  it  will  be  observed  that  the  level 
of  the  .solution  of  magnesium  sulphate  has  risen  a  considerable  distance. 
The  solution  of  magnesium  sulphate  possesses  a  greater  osmotic  press- 
ure and  draws  mokx'ules  of  water  through  the  membrane. 

2.  The  Osmotic  Power  of  the  Intestine. — Anesthetize  a  cat  and 
maintain  the  anesthesia  until  the  animal  has  been  killed  by  an  overdose 
of  ether.  Perform  tracheotomy.  Open  the  abdominal  cavity  by  a 
small  longitudinal  incision  in  the  linea  alba.     Pull  a  loop  of  small  in- 

217 


218         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

testine  about  20  cm.  in  length  through  this  opening.  The  jejunum  is 
usualh'  empty.  If  not,  gently  squeeze  its  contents  along  into  the 
lower  bowel.  Tie  a  ligature  tightly  about  the  middle  of  the  exposed 
segment,  and  a  second  and  third  about  8  cm.  distally  and  centrally  to 
this  one.  In  this  way  two  segments  of  intestine  have  been  isolated. 
Into  one  of  these  inject  5  c.c.  of  a  saturated  solution  of  magnesium  sul- 
phate, and  into  the  other  30  c.c.  of  a  0.7  per  cent,  solution  of  sodium 
chlorid.  Note  that  the  former  segment  feels  perfectly  empty,  whereas 
the  latter  is  highly  distended.  Replace  the  entire  loop  in  the  abdominal 
cavity,  marking  its  upper  end  with  a  colored  piece  of  cord.  Close  the 
opening  in  the  abdominal  wall  with  a  clamp.  Cover  the  animal  with 
a  warm  cloth  and  allow  it  to  rest  under  anesthesia  for  thirty  minutes. 
At  the  end  of  this  period  expose  the  aforesaid  segments  and  determine 
their  degree  of  distention.  It  will  now  be  found  that  the  loop  contain- 
ing the  Mg  SO4  is  highly  distended,  whereas  the  loop  with  the  NaCl  is 
practically  empty.  Obviously,  the  Mg  SO4,  possessing  a  greater  osmotic 
pressure  than  the  body  fluids,  has  abstracted  water  from  the  latter. 
Contrariwise,  the  0.7  per  cent,  solution  of  NaCl  has  been  removed  from 
the  loop.  Using  these  facts  as  a  basis,  explain  the  action  of  the  saline 
cathartics. 

3.  Chemical  Stimulation  of  the  Secretion  of  Intestinal  Juice. — 
Insert  a  cannula  in  the  external  jugular  vein,  and  empty  a  loop  of 
duodenum  about  30  cm.  in  length.  Inject  intravenously,  from  1  to 
3  c.c.  of  M/8  solution  of  barium  chlorid  or  sodium  citrate.  Observe 
the  peristalsis  which  results  almost  immediately  and  measure  the 
quantity  of  intestinal  juice  obtainable  from  this  segment.  Kill  the 
animal  by  an  excessive  amount  of  ether. 

4.  Gastric  Fistula. — Procure  curved  needles,  a  needle-holder,  and 
clamps.  Bring  the  wall  of  the  pylorus  in  the  wound  and  anchor  it  by 
means  of  a  continuous  suture.  Decrease  the  length  of  the  wound  by 
sutures.  Incise  the  gastric  wall  and  suture  it  to  the  edges  of  the  wound. 
Insert  a  gastric  cannula  and  secure  it  by  additional  sutures. 

5.  Peristalsis. — Anesthetize  a  rabbit  and  maintain  the  anesthesia 
during  the  following  experiments  and  until  the  animal  has  been  killed 
by  an  overdose  of  ether.  Perform  tracheotomy.  Open  the  abdominal 
cavity  by  a  median  incision  through  the  linea  alba.  Observe  the 
peristalsis.  The  intestine  of  the  rabbit  invariably  shows  most  intense 
peristaltic  movements  when  exposed  to  the  cooler  air  or  stimulated 
mechanically.  Note  the  pendular  movements  and  also  the  regular 
peristalsis. 

Compare  the  length  and  general  appearance  of  the  intestines  of  the 
rabbit  with  those  of  the  intestines  of  the  cat  and  dog,  noting  especially 
the  predominance  of  the  large  intestine  in  the  former  animal.  Discuss 
the  functional  significance  of  this  difference. 

6.  The  Influence  of  Salts  on  Peristalsis. — Apply  a  few  drops  of 
M/320  solution  of  barium  chlorid  or  sodium  citrate  to  the  peritoneal 
surface  of  a  loop  of  intestine.     Observe  the  marked  peristalsis  which 


AliSUUPTION  219 

follows.     Inhibit    this   inovciucnt    by   applying  a  solution   of   cjilciiiru 
chlorid  or  ina^;n('siuin  chloric  I. 

7.  Secretion  of  Intestinal  Juice  into  Excised  Loops. — Empty  a  loop 
of  small  intestine  about  10  cm.  in  length  by  j^cntlc  pressure  exerted  with 
your  fingers.  Place  two  pairs  of  ligatuios  around  the  intestine  so  as  to 
isolate  this  segment.  Ligate  the  corresponding  blood-vessels.  Re- 
move this  segment  from  the  body  by  cutting  between  each  pair  of 
ligatures.  Kill  the  animal  by  an  overdose  of  ether.  Suspend  the  ex- 
cised loop  at  38°  C.  in  a  measured  quantity  of  M/8  sodium  chlorid  to 
which  from  one-seventieth  to  one-fiftieth  of  its  volume  of  M/8  barium 
chlorid  has  be(>n  added.  Keep  the  ends  of  the  intestinal  segment  above 
the  surface  of  the  solution.  Observe  the  peristalsis.  After  about 
twenty  minutes  measure  the  quantity  of  fluid  which  has  been  secreted 
into  the  lumen  of  the  segment.  Since  the  quantity  of  the  fluid  surround- 
ing this  loop  has  not  been  lessened,  the  secretion  must  have  been 
formed  from  the  material  stored  in  the  cells  at  the  time  of  their  removal 
from  the  body. 

8.  Influence  of  Adrenal  Extract  on  Intestine. — Remove  a  piece  of 
duodenum,  al)out  10  cm.  in  length,  and  place  it  in  cold  Ringer's  solu- 
tion. After  a  time  cut  off  a  piece  2  cm.  in  length  and  suspend  it  in  a 
beaker  filled  with  Ringer's  solution.  Connect  its  lower  end  with  a 
weight  placed  upon  the  bottom  of  the  receptacle  and  its  upper  end 
with  a  writing  lever  properly  counterpoised. 

Place  a  small  flame  underneath  the  beaker  and  slowly  raise  the 
temperature  of  the  fluid  to  30°  C.  Start  the  recording  drum  and  reg- 
ister the  movements  of  this  strip. 

Add  0.5  c.c.  of  adrenalin  to  the  Ringer  fluid  (300  c.c).  Note  the 
effect  upon  the  length  of  the  strip  (tonus)  as  well  as  upon  its  con- 
tractions. 

9.  Rapidity  of  Absorption  and  Elimination. — Into  each  of  ten  test- 
tubes  pour  5  c.c.  of  thin  starch  paste  and  2  c.c.  of  concentrated  nitric 
acid.  Swallow  a  capsule  containing  10  grains  of  potassium  iodid  and 
rinse  your  mouth  thoroughly.  Increase  the  secretion  of  saliva  by  ch(>w- 
ing  a  piece  of  paraffin  and  collect  at  intervals  of  two  minutes  a  quantity 
of  saliva  in  the  corresponding  test-tubes.  Rinse  the  mouth  after  each 
collection.  How  soon  after  ingestion  can  this  agent  be  recognized  in 
the  saliva? 

10.  Histologic  Examination  of  Preparations  of  Intestinal  Mucosa. — 
Study  the  structure  of  a  villus,  mucous  cells,  and  glands  of  Lieberklihn. 


LESSON  XLVIII 

EXCRETION 

SECRETION  OF  URINE 

1.  The  Drop  Method  of  Registering  the  Flow  of  Urine. — Anesthetize 
a  mammal  and  continue  the  anesthesia  throupihout  the  followinfj;  experi- 
ments: Perforin  trachelotomy.  Expose  the  left  common  carotid  artery 
and  insert  in  it  a  strai,u:ht  glass  cannida.  Fill  it  with  a  solution  of  sodium 
carbonate,  and  connect  it  with  the  mercury  manometer.  Isolate  the 
vagus  nerve  on  the  same  side  and  place  it  in  a  loose  silk  ligature.  On 
the  opposite  side  expose  the  external  jugular  vein.  Clamp  it  centrally; 
hgate  it  about  2  cm.  distally  to  the  clamp,  and  insert  a  straight  glass 
cannula  toward  the  heart.     Fill  this  cannula  with  normal  saline  solution. 

Open  the  abdominal  cavity  in  the  linea  alba  below  the  umbilicus. 
Identify  the  bladder  and  the  two  ureters  leading  awa.y  from  its  posterior 
surface.  Insert  a  straight  cannula  in  each  (toward  the  kidney)  and 
connect  them  by  means  of  short  pieces  of  ru))ber  tubing  with  a  Y-tube. 
Allow  the  end  of  the  Y-tube  to  project  beyond  the  edge  of  the  board,  at 
a  distance  of  about  20  cm.  above  the  spoon-shaped  lever  of  the  receiving 
tambour.  Connect  the  latter  by  means  of  a  long  piece  of  rubber  tub- 
ing with  a  recording  tambour  placed  against  the  paper  of  the  kymograph. 
Adjust  the  recording  needle  of  the  mercury  manometer  in  such  a  way 
that  it  registers  in  the  same  ordinate  as  the  writing  lever  of  the  record- 
ing tambour.  Allow  a  chronograph  to  register  seconds  below  these 
levers. 

2.  Normal  Secretion  of  Urine. — Allow  the  kymograph  to  revolve  at 
a  moderate  speed,  and  register  the  drops  of  urine  secreted  in  relation 
with  the  curve  of  the  blood-pressure.  Remember  that  the  formation  of 
urine  is  often  greatly  lessened  during  ether  narcosis.  If  this  condition 
prevails  in  the  animal  used  for  this  experiment,  stimulate  the  flow  in 
the  manner  described  in  paragraph  3. 

3.  Action  of  Glucose.^ — Prepare  a  concentrated  solution  of  glucose 
(25  c.c).  Filter  it  and  draw  10  c.c.  of  the  filtrate  into  a  pipet.  Con- 
nect the  latter  with  the  cannula  inserted  in  the  external  jugular  vein. 
Allow  this  quantity  of  glucose  to  enter  the  circulation,  but  slowly,  so 
that  the  height  of  the  blood-pressure  is  not  altered.  After  a  certain 
latent  period  drops  of  urine  will  be  seen  to  enter  the  Y-tube  at  intervals. 
Observe  the  rapidity  with  which  they  are  secreted.  It  is  said  that 
glucose  stimulates  the  renal  cells  directly,  giving  rise  to  diuresis. 
Record  the  flow  in  relation  with  the  blood-pressure. 

4.  Action  of  Sodium  Chlorid.— When  the  diuresis  produced  by  the 
glucose  has  nearly  subsided,  inject  100  c.c.  of  warmed  saline  solution. 
Register  the  flow  of  urine  in  the  manner  described  above.  Repeat  the 
injection  if  the  effect  is  not  sufficiently  decisive. 

221 


222         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

The  injection  of  so  large  a  quantity  of  solvent  is  prone  to  produce  a 
material  rise  in  the  blood-pressure,  thereby  increasing  the  filtration 
pressure.  For  this  reason  the  diuretic  effect  of  sodium  chlorid  is  fre- 
quently referred  to  this  cause,  in  combination  with  hydremia  and 
osmotic  changes,  and  not  to  a  direct  stimulating  action  upon  the  renal 
cells. 

5.  Effect  of  Changes  in  Blood-pressure. — When  an  active  secretion 
has  been  produced,  stimulate  the  vagus  nerve,  thereby  evoking  a 
material  reduction  in  the  general  blood-pressure.  While  the  secretion 
of  urine  is  then  greatly  lessened,  note  that  the  flow  does  not  return  to 
normal  until  a  considerable  time  after  the  cessation  of  the  stimulation. 
This  fact  tends  to  show  that  while  the  blood-pressure  is  an  important 
factor  in  the  production  of  urine,  the  secreting  cells  are  not  dominated 
by  pressure  alone. 

Dilute  a  1  :  1000  solution  of  adrenahn  sufficiently  to  cause  a  moder- 
ate rise  in  blood-pressure  (2  c.c.  of  the  solution  to  20  c.c.  of  sahne). 
Register  the  flow  of  urine.     Inject  a  small  quantity  of  the  aforesaid 


Fig.   123. — Effect  of  Stimulation  of  the  Vagus  Nerve  Upon  the  Secretion  of 

Urine. 

solution  of  adrenalin  in  the  external  jugular  vein.  Note  that  the  flow 
of  urine  is  greatly  lessened  thereby  in  spite  of  the  high  blood-pressure. 
This  discrepancy  is  easilj'-  explained,  because  the  adrenalin  constricts 
the  blood-vessels  of  the  kidney,  and  gives  rise  to  a  lessened  vascularity 
of  this  organ  and  lessened  secretory  power  of  its  cells. 

6.  Rapidity  of  Elimination. — Prepare  a  saturated  solution  of  indigo- 
carmin.  Inject  5  c.c.  of  this  solution  in  the  external  jugular  vein,  not^ 
ing  the  moment  of  the  injection.  Again  determine  the  time  when  this 
pigment  appears  in  the  urine.     Kill  the  animal  by  an  overdose  of  ether. 

7.  Dissection  of  the  Region  of  the  Kidney. — Identify  the  suprarenal 
bodies  on  each  side.  Carefully  remove  the  left  organ  and  expose  the 
suprarenal  plexus,  greater  and  lesser  splanchnic  nerves,  and  fibers  of 
the  renal  plexus. 

Open  the  pelvis  of  the  kidney  and  study  the  characteristics  of  the  cut 
surface  of  this  organ.  Identify  the  papillae,  pyramids,  medulla,  cortex, 
and  capsule.  Remove  the  capsule.  Is  it  closely  adherent  to  the  sub- 
stance of  the  kidney? 


LESSON  XLIX 

EXCRETION  (Continued) 

SECRETION  OF  SWEAT.     BODY  TEMPERATURE 

1.  Sweat  Nerves.  Am'stlu'tizc  ii  cut  and  iiuiintain  the  anesthesia 
until  the  animal  has  l)(>en  killed  by  an  overdose  of  ether.  Expose  the 
sciatic  nerve,  apply  a  ligature,  and  cut  centrally  to  the  liji;ature.  Stiniu- 
late  the  distal  end  of  the  divided  nerve  with  a  quickly  interrupted  current 
of  moderate  intensity.  Observe  the  beads  of  sweat  collecting;  upon  the 
pads  of  the  feet.  Take  the  rectal  tenipeiature  of  this  animal.  Apply 
a  cloth  moistened  with  warm  water  to  the  upper  part  of  its  body, 
thereby  raising  its  body  temperature.  Sweating  is  also  evoked  by  this 
means.     Explain  its  purpose. 

Expose  the  external  jugular  vein  and  inject  3  milligrams  of  atropin 
sulphate.  Note  that  the  stimulation  of  the  sciatic  nerve  now  remains 
ineffective.     The  atropin  paralj'zes  the  secretory  nerve  endings. 

Inject  10  milligrams  of  pilocarpin.  Sweat  will  again  be  secreted,  be- 
cause this  agent  excites  the  cells  of  the  sweat-glands  directly.  Kill  the 
animal  by  an  o\'er(lose  of  ether. 

2.  Sweating  in  Man. — Procure  a  piece  of  paper  sensitized  with 
silver  nitrate.  Cleanse  the  pahn  of  the  hand  and  after  a  certain  interval 
appl}^  the  paper  to  this  surface.  The  orifices  of  the  sweat-glands  will 
be  marked  upon  the  paper  as  spots  of  silver  chlorid.  Apply  to  this 
area  a  small  pad  of  cotton  moistened  with  a  1  per  cent,  solution  of  atropin 
sulphate.  Repeat  the  aforesaid  test.  Since  atropin  paralyzes  the  end- 
ings of  the  secret(My  nerVes,  this  test  will  now  remain  negative. 

3.  Body  Temperature.— Determine  the  body  temperature  of  the 
subject  by  means  of  an  ordinar}^  thermometer,  the  bulb  of  which  is 
placed  beneath  the  tongue.  Ask  the  subject  to  close  the  lips.  Observe 
the  rapidity  with  which  the  temperature  becomes  constant.  How  long 
a  time  must  the  thcM-mometer  be  left  iti  situ  before  the  mercury  remains 
stationary? 

Determine  the  axillary  temperature  in  the  same  manner.    Compare. 

Place  the  bulb  of  the  thermometer  in  the  palm  of  the  closed  hand. 
Read  the  temperature.  Compare,  Wrap  the  hand  in  a  thick  woolen 
cloth.  Why  is  the  temperature  now  higher?  Place  the  same  hand  in 
water  of  20°  C.  for  thirty  seconds.  Again  determine  its  temperature. 
Explain  the  result. 

Request  the  subject  to  make  thirty  flexions  of  the  arms  and  legs. 
Quickly  determine  the  body  temperature.  For  how  long  a  time  does 
the  rise  persist? 


223 


LESSOX  L 

EXCRETION  (Concluded) 

THE  INNERVATION  OF  THE  BLADDER.     PILOMOTOR  REACTIONS 

1.  The  Function  of  the  Hypogastric  Nerves. — Anesthetize  a  cat  and 
maintain  the  anesthesia  throujihout  the  following  experiments:  Per- 
form tracheotomy.  Open  the  alxlominal  cavity  by  a  median  incision 
in  th(>  linea  alba.  Itlentify  the  urinary  bladder,  and  raise  its  fundus 
sufficiently  to  expose  the  fatty  tissue  investing  its  cervical  portion. 
By  careful  dissection  isolate  th(^  nerve-fibers  which  ascend  from  here  to 
the  fundus.  Place  them  in  shielded  electrodes,  and  arrange  the  elec- 
tric apparatus  for  stimulation  with  a  tetanizing  current  of  medium 
strength. 

Insert  a  small  hook  in  the  top  of  the  fundus  of  the  bladder  and 
connect  it  by  means  of  a  thread  with  the  end  of  a  writing  lever  (suspen- 
sion method).  Counterpoise  the  lever  so  as  to  place  the  musculature 
of  the  bladder  under  a  certain  tension.  Place  cotton  moistened  with 
warm  saline  solution  around  the  base  of  the  bladder  to  protect  the 
abdominal  organs  against  evaporation  and  thermal  influences.  Allow 
the  drum  to  revolve  at  a  slow  rate  and  stimulate  the  hypogastric  fibers 
until  a  contraction  of  moderate  height  has  been  obtained. 

Cut  one  nerve  and  stimulate  the  central  end  of  this  nerve.  Note 
that  the  bladder  is  now  made  to  contract  reflexly  through  the  hypo- 
gastric center  and  intact  nerve  on  the  opposite  side. 

2.  Pilomotor  Efifects. — Unite  the  margins  of  the  wound  in  the 
abdomen  l)y  a  few  sutures.  Make  a  median  incision  through  the  skin 
covering  the  base  of  the  tail  and  posterior  extent  of  the  vertebral 
column.  Reflect  the  muscles.  Clip  away  the  spinal  processes  and 
adjoining  laminse  of  several  vertebrse  near  the  base  of  the  tail.  Apply 
a  cotton  tampon  until  the  bleeding  has  stopped.  Incise  the  dura 
mater  and  identify  the  chorda  equinse.  Isolate  several  of  its  constituent 
nerve-fibers  close  to  the  base  of  the  tail  and  place  them  in  loose  liga- 
tures. Smooth  the  hairs  of  the  tail  and  place  the  latter  upon  a  sheet 
of  white  paper.  Note  its  volume.  Stinnilate  the  nerve-fibers  just 
isolated  successively^  with  a  weak  tetanizing  current,  until  one  is  found 
which  causes  an  erection  of  the  hairs  of  the  tail.  Again  smooth  the 
tail  and  repeat  this  experiment.  Explain  the  mechanism  by  which 
hairs  are  erected.  Kill  the  animal  by  an  overdose  of  ether.  Repeat 
the  stimulation  of  these  pilomotor  fibers  after  an  interval  of  several 
minutes.  Note  that  this  mechanism  remains  effective  for  some  time 
after  death. 


15  225 


DEMONSTRATIONS   TO   BE   GIVEN   IN   CONNECTION   WITH 
THE  PRECEDING  LESSONS 

1.  (a)  The  dcterinination  of  the  strcngtli  of  tlic  make  and  break 

incliu'tioii  shocks  by  means  of  the  galvanometer.     Pro- 
jection method. 
(6)  The  procUiction  of  acid  in  contracting  nmscle.    Acid  fuclit;in 
method. 

2.  Electrotonus.     Pfliiger'.s  law  of  contraction. 

3.  The  current  of  injury  and  current  of  action  in  muscle  and  nerve. 
Projection  method. 

4.  The  action  of  electric  currents  of  high  voltage. 

5.  (a)  Extraction  of  the  gases  of  the  blood  by  means  of  the  mer- 

cury pump.     Baicroft-Haldane  blood-gas  apparatus. 
(6)  ^'iscosinleter  (Burton-Opitz). 

6.  (a)  Projection  of  the  spectrum.     Formation  of  the  bands  of 

oxyhemoglobin  and  reduced  hemoglobin. 
(6)  The  capillary  circulation  in  the  mesentery  or  bladder  of  the 
frog.     Projection  method. 

7.  (a)  The  action  of  the  valves  of  the  heart.     Gad's  method. 
(6)  The  vitelline  area  in  the  developing  chick. 

8.  (a)  The  construction  and  action  of  different  types  of  galvan- 

ometers. 
(6)  Einthoven's  string  galvanometer  and  the  action  current  of 
the  heart. 

9.  Electrocardiography.     Normal  and  abnormal  records. 

10.  The  registration  of  the  sounds  of  the  heart.  Normal  and  ab- 
normal records. 

11.  The  effect  of  increases  in  intracranial  pressure  upon  the  circula- 
tion and  respiration. 

12.  The  blood-supply  of  the  intestines,  demonstrated  by  means  of 
the  recording  stromuhr  of  Burton-Opitz.  Stimulation  of  the  splanchnic 
nerve. 

13.  The  vasomotor  function  of  the  spinal  cord.  Division  and 
stimulation  of  the  cord. 

14.  Fluoroscopic  examination  of  the  heart  and  lungs  in  man. 

15.  Perfusion  of  the  excised  mannnalian  heart. 

16.  The  application  of  the  polygraph  (Mackenzie). 

17.  Projection  of  the  larynx.  Stimulation  of  the  superior  and  in- 
ferior laryngeal  nerves. 

18.  Abolished  and  exaggerated  reflexes  in  man  in  consequence  of 
"high''  and  "low"  lesions  of  the  nervous  sj'stem. 

19.  (a)  The  decerebrated  pigeon. 
(6)  The  decerebrated  cat. 


228         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

20.  (fl)  Lesions  of  the  cerebellum  in  pigeons. 
(6)  Cerebellar  defects  in  man.     Nj'stagmus. 

21.  (a)  Stimulation  of  the  semicircular  canals  in  the  turtle. 
(6)  Lesions  of  the  semicircular  canals  in  pigeons. 

22.  Hemiplegia,  aphasia,  and  hemianopsia  in  man. 

23.  The  dissociation  of  the  cutaneous  sensations.     Syringomyelia. 
Sensory  anesthesia. 

24.  The  accommodation  of  the  eye  of  the  frog,  turtle,  and  fish. 

25.  (a)  Large  demonstration  ophthalmoscope. 

(6)  Astigmatism  determined  by  means  of  the  ophthalmotonom- 
eter of  Helmholtz. 

26.  Myopia  and   hypermetropia   displayed   by  means   of  a  large 
Kiihne's  artificial  eye. 

27.  Fluoroscopic  observation  of  the  movements  of  the  stomach  and 
intestines  in  a  mammal. 

28.  Removal  of  the  thyroid  and  parathyroid  bodies. 

29.  Removal  of  the  suprarenal  bodies. 

30.  (a)  Dog  with  gastric  fistula. 

(6)  Diffusion  demonstrated  with  the  help  of  the  apparatus  de- 
scribed by  Abel. 


WEIGHTS  AND  MEASURES* 

In  the  niPtric  syt^ti-ni  the  liter  is  a  unit  (if  caparity  cquivalont  to  the  volume 
occupied  hv  the  mass  of  1  kilogram  of  pure  water  at  its  maximum  density.  It  is 
equivalent  in  volume  to  l.()()(M)27  cubic  decimeter.  Under  this  definition  a  milli- 
liter (0.001  of  a  liter)  i.s  different  from  a  cubic  centimeter  by  a  verv  minute  frac- 
tion. However,  as  "cubic  centimeter"  is  the  term  u.sed  throughout  medical  literature 
we  shall  use  it  in  this  book,  though  both  the  U.  S.  and  British  Pharmacopoeias  have 
adopted  the  term  "milliliter"  (.niil)  i"  its  place. 


A.  METRIC 

_,   .   ,  Approximate 

n  eight:                                                                                                        Writtin.  i'<iuivalent. 

1  milligram  (mg.) 0.(X)1  g'-  grain 

10  milligrams  =  1  centigram  (eg.) 0.01  e  grain 

10  centigrams  =  1  decigram  (dg.) 0.1  1',  grains 

10  decigrams  =  1  gram  (gm.) 1.0  1.5  grains 

1000  grums  =  1  kilogram  (kilo.) 1000.0  21  pounds 

Volutne: 

1  milliliter  (mil.) 1.0  15  minims 

1  cubic  centimeter  (c.c.) 1.0  15  minims 

(1  c.c.  of  water  weighs  1  gm.) 

1000  cubic  centimeters  =  1  Uter  (L.) 1000.0  34  fluidounces 

Length: 

1  millimeter  (mm.) -^  inch 

10  millimeters  =  1  centimeter  (cm.) ?  inch 

10  centimeters  =  1  decimeter  (dm.) 4  inches 

10  decimeters  =  1  meter  (M.) 40  inches 

B.  APOTHECARIES 

TT'   ■   1.1  rrr       \  Approximate 

Weight  (Troy):  equivalent. 

1  grain  (gr.) 0.065  gm. 

10  grains 0.7      gm. 

20  grains  =  1  scruple  (3) 1.3      gm. 

3  scruples  =  1  dram  (3) 4.0      gm. 

8  drams  =  1  ounce  (3 ) 30.0      gm. 

12  ounces  =  1  pound  (lb) 372.0      gm. 

Volume: 

1  minim  (itr) 0.06    c.c. 

60  minims  =  1  dram  (3) 4.0      c.c. 

S  drams  =  1  ounce  (5) 30.0      c.c. 

16  ounces  =  1  pint  (O) 475.0      c.c. 

2  pints  =  1  quart  (Oij) 950.0      c.c. 

8  pints  =  1  gallon  (Cong.). 

(1  gill  =  4  fluidounces.) 

Length : 

1  inch  (in.) 2.5      cm. 

*  From  Bastedo's  "Materia   Medica,  Pharmacology,  Therapeutics,  and  Pre- 
scription Writing." 

229 


230         ADVANCED  LESSONS  IN  PRACTICAL  PHYSIOLOGY 

Approximate 
Noteworthy  lerms:  equivalent. 

1  ounce  avoirdupois 437.5  grains 

1  ounce  troy 480.0  grains 

1  fluidounce  of  water  (the  standard  of  volume) 455.7  grains 

1  pound  avoirdupois  is 7000.0  grains 

1  pound  troy  is 5760.0  grains 

1  minim  of  water  weighs  -^^  grains  =  0.95  grain  =  61.61  mg. 

15  grains  of  water  =  16  minims;  1  grain  of  water  measures 

1.05  minims  =  0.0648  c.c. 
An  imperial  pint  is  20  ounces;  a  United  States  pint  is  16  oimces. 

EXACT  EQUIVALENTS  OF  METRIC  AND  APOTHECARIES'   WEIGHTS 
AND  MEASURES  ACCORDING  TO  THE  U.  S.  PHARMACOPCEIA 

,  ■  Approximate 

\  otume:  equivalent. 

1  C.C 16.23    minims 

1  Uter  (1000  c.c.) 33.8     oz. 

1  minim   (nji) 0.061  c.c. 

1  fluidram  (3) 3.696  c.c. 

1  fluidounce  (5 ) 29.57    c.c. 

1  pint  (0) 473.18    c.c. 

Weight: 

1  milligram,  0.001  (mg.) 0.0154  grain 

1  centigram,  0.01  (eg.) 0.1543  grain 

1  decigram,  0.1  (dg.) 1.543    grains 

1  gram,  1.0  (gm.) 15.4324  grains 

30  grams,  30.0 462.9        grains 

31  grams 478.4        grains 

1  grain  (gr.) 0.065    gm. 

10  grains 0.648  gm. 

15  grains 0.972  gm. 

1  scruple  O) 1.296  gm. 

1  dram  (5) 3.89  gm. 

1  ounce  troy  (§) 31.1  gm. 

1  ounce  avoirdupois 28.35  gm. 


INDEX 


Abdominal  aorta,  compression  of,  107 
Abduction  of  vocal  cords,  143 
Aberration,  achromatic,  1S9 

spheric,  190 
Absorption,  217 

and  ehmination,  rapidity  of,  219 
Acceleration  of  heart,  88 
Accommodation  reflex.  184 
Achromatic  aberration,  189 
Action  current  of  frog's  heart,  00 
of  muscle,  59 
of  nerve,  60 

of  cocain,  167 

of  glucose,  221 

of  secretin,  214 

of  sodiimi  chlorid,  221 
Acuity  of  dynamic  sense,  180 

of  temperature  sense,  170 
Adaptation  to  touch  sensations,  lOS 
Adduction  of  vocal  cords,  143 
Adrenal  extract,  influence  of,  on  inte- 

tine,  219 
Adrenalin,   effect   of,  on  blood-pressure, 

110 
Afl'erent  impulses,  summation  of,  157 
After-images,  negative,  201 

of  temperature,  169 

positive,  200 
Air,  entrance  of,  into  circulation,  115 
All-or-none  law,  82 
Ameboid  motion,  21 

Ametro))ic  artificial  eye,  ophthalmoscopic 
examination  of,  by  direct  method, 
195 

eye,  188,  189 
Amyl   nitrite,   effect   of,   on   blood-pres- 
sure. 110 
Anelectrot'  nus,  63 
Anodic  excitation  of  nerve,  64 
Aorta,  abdominal,  compression  of.  107 
Aortic  insufficiency,  schema  of,  102 

stenosis,  schema  of,  102 
Apex-beat  of  heart,  95 
Apothecaries'  weight,  229 
exact  equivalent,  230 
Aristotle's  experiment,  167 
Arterial  blood.  68 

blood-pressure,  direct    method   of  de- 
termining, 103 

pulse,  character  and  velocity.  129 
heart  action  and  relation  between,  129 


Artificial    eye,     ametropic,     ophthalmo- 
scopic   examination    of,  by  direct 
method,  195 
emmetropic,     ophthalmoscopic     ex- 
amination  of,  by   direct  method, 
194 
opthalmoscopic  examination  of,  by 
indirect  method,  196 
respiration,  140 
Asphyctic  blood,  68 
Asphyxia.  135 

Associated  movements  of  eyes,  200 
Astigmatism,  189 
detection  of,  194 
measurement  of,  194 
Atmospheric  pressure,  decreased,  effect  on 

lungs,  148 
Atropin,  action  on  heart,  87 
Auditory  fatigue,  174 
Auscultation,  139 

Axes,  visual,  convergence  of,  influence  of, 
203 


Babinski  phenomenon,  eliciting,  160 
Bile,  secretion  of,  215 
Binocular  fusion  of  dissimilar  images,  203 
vision,    relation    of,    to   judgments   of 
direction,  203 
of  distance,  203 
of  solidity.  203 
Bladder,  innervation  of,  225 
Blind  spot,  199 

contours  of.  199 
Blood,  arterial.  68 
asphyctic,  68 

cells,  red,  human,  counting  of,  73 
chemical  tests  for,  78 
coagulation  of,  69 
corpuscles,  red,  enumeration,  70 
simultaneous  count,  73 
relative  amounts,  70 
white,  enumeration  of,  71 
simultaneous  count,  73 
crystals,  78 
experiments  on,  preparation  of  animal 

for,  67 
flow  through  lungs,  effect  of  variations 
in  intrathoracic  pressure  on,  147 
velocity   of,    differences   in,   schema 
illustrating,  103 

231 


232 


INDEX 


Blood,  medicolegal  tests  for,  77 
microscopic  examination,  73 
plai^ma,  relative  amounts,  70 
specific  gravity,  75 
spectroscopic  examination  of,  77 
suspected,  examination,  78 
venous,  68 
Bloodless  gland,  secretion  by,  210 
Blood-pressure,  arterial,  direct  method  of 
determining,  103 
carotid,  record  of,  113 
effect  of  adrenalin  on,  110 
of  amyl  nitrite  on,  110 
of  changes  in,  222 
of  division  of  both  vagi  nerves  on,  114 

of  one  vagus  nerve  on,  114 
of  exercise  on,  128 
of  hemorrhage  and  sahne  injection 

on,  111 
of  posture  on,  127 

of  stimulation  of  intact  vagi  nerves 
on, 113 
estimation  by  indirect  method,  125 
influence  of  dyspnea  on,  109 
of  hemorrhage  on,  108 
of  posture  on,  107 
intracarcUac,  115 
venous,  128 
Blood-supply,    influence   of,    on    muscle 

contraction,  52 
Blood-vessels,  retinal,  199 
Body  temperature,  223 
Bones,  manner  of  attachment  of  muscles 
to,  39 


Capillary  circulation,  99 

in  frog's  lung,  147 
Carbon    dioxid,    elimination   of,    in   res- 
piration, 151 
influence  of,  in  respiration,  140 
Cardiac  plethysmograph,  92 
Cardiogram,  96 
Cardiograph,  96 
Cardiometer,  92 

Carotid  blood-pressure,  record  of,  113 
Catelectrotonus,  63 
Cathodic  excitation  of  nerve,  64 
Cell,  Daniell,  25 

dry,  construction  and  action,  25 
Cerebral  localization,  163 
Cerebrum,  influence  of,  162 

removal  of,  effect,  161 

stimulation  of,  163 
Cervical   sympathetic  nerve,   vasomotor 

action,  117 
Chemical    and    electric    stimulation    of 
temperature  spots,  169 

stimulation  of  muscle,  47 

of  secretion  of  intestinal  juice,  218 

tests  for  blood,  78 
Chemicals,  influence  of,  on  muscle  con- 
traction, 48 
Chloroform    and    ether,    action    of,    on 

heart,  90 


Chorda  tympani  nerve,  function  of,  210 
Chyle,  215 
Ciliary  motion,  21 
Circles  of  dispersion,  188 
Circuit,  primary,  29 

secondary,  30 
Circulation,  capillary,  99 
in  frog's  lung,  147 
constant-flow,  99 
entrance  of  air  into,  115 
in  frog's  lung,  147 
intermittent  flow,  99 
schema,  normal,  101 
remittent  flow,  99 
schema,  100 
Coagulation  of  blood,  69 
Cocain,  action  of,  167 
Coil,  induction,  29 

Cold  and  hot  spots,  mechanical  stimu- 
lation of,  169 
thermal  stimulation  of,  169 
Cold-blooded    animals,    speed    of    nerve 

impulse  in,  55 
Collapse  of  lung,  136 
Collection  of  pa^ncreatic  juice,  213 
Color-blindness,  202 
Colored  objects,  fields  for,  191 
Colors,  complementary,  202 
contrast,  202 
fusion  of,  201 
Commutator,  Pohl's,  56 
Complementary  colors,  202 
Conductivity  of  nerve,  36 
Constant  current,  29 
Contraction,  muscle,  compound,  43 

effect  of  excessive  stimulation  on,  49 
of  veratrin  on,  49 
on  volume,  38 
fusion  of,  42 

height  of,  relation  of  amount  of  load 
to,  44 
of  strength  of  stimulus  to,  43 
human,  51 

influence  of  blood-supply  on,  52 
of  chemicals  on,  48 
of  temperature  changes  on,  47 
method  of  registering,  33 
paradoxic,  60 
single,  41 
summation  of,  42 
Contrast  colors,  202 
Convergence  of  visual  axes,  influence  of, 

203 
Corpuscles,  blood.     See  Blood  corpuscles. 
tactile,  histologic  examination  of,  167 
Crystals,  blood,  78 

hemin,  78 
Currents,  electric,  types,  28 
Cutaneous  and  muscular  sensations,  167 


Daniell  cefl,  25 
Deglutition,  207 

in  human  subject,  208 

wave  of,  207 


INDKX 


233 


Doprossor  norvo,  vasomotor  action  of,  1  is 
Diaplir.iniu,  action  of,  liio 
Didncoii  s|ilivniiiofirapli,  \'2\) 
Digestion,  2('»7,  'JO'.t,  2i;{.  21.") 
Din'<'t  and  indirect  vision,  200 

method  for  opiitlialnioscopic  examina- 
tion   of    ametropic    artiliciai 
eye,  195 
of  emmetropic  artificial  eye,  I'.M 
Direction,     judjiments     of,     relation     of 

binocnlar  vision  to,  203 
Discrimination  of  weight,   Weber's  law, 

170 
Dispersion,  circles  of,  l.SiS 
Dissection  of  ear  of  dog-fish,  179 

of  eye,  1S3 

of  region  of  kidney,  222 

of  salivary  glands,  211 
Distance,   judgment  of,  relation   of   bin- 
ocular vision  to,  203 
Double  and  single  images,  203 
Drop  method  of  registering  flow  of  urine, 

221 
Dry  cell,  construction  and  action,  25 
Dynamic  and  static  senses,  179 

sense,  acuity  of,  180 
Dynamometer,  52 
Dyspnea,  135 

influence  of,  on  bl()oil-i)ressur(>,  109 


Ear.  diagrammatic  representation  of,  170 

middle,  models  of,  175 

of  dog-Hsh,  dissection  of,  179 
Elbow,  sensation  of  motion  at,  171 
Electric    and    chemical    stimulation    of 
temiK-rature  spots,  169 

currents,  types,  2S 

stimulation  of  muscle,  23 
Electrodes,  non-polarizable,  29 

stimulating,  27,  28 
Electrotonus,  G3 
Elimination  and  absorption,  rapiditj-  of, 

219 
^  rapidity  of,  222 

Emmetropic  artificial  eye,  ojihthalmo- 
scopic  examination  of,  bv  direct 
method,  194 

eye,  187 
Entoptic  phenomena  produced  bv  tears, 

192 
iMjuilibrium  a  combined  .s(>nse,  181 
Ergograph,  Mosso's,  51 

si)ring,  .52 
Ergographic    record    of    frog's    gastroc- 
nemius, 52 
Esophagus,  division  of,  207 

isolation,  207 
Esthesiometer,  167 
Ether  and  chloroform,  action  on  heart, 

90 
Excised  heart,  82 
Excitation  wave  of  heart,  transmission  of, 

81 
Excretion,  221,  223,  225 


Ivxercise,  elTect  of,  on  blood-pressure,  12S 
ivxperimental  jaundice,  210 
I'vXlensibilit  V  of  muscle,  30 
Exlnisystole,  Si 
lOye,  anielro|)ie,  18.S,  189 

dissection  of,  18.3 

emmetropic,  1,S7 

artiliciai,  o|)litli;dmoscopic  examina- 
tion of,  by  direct   method,  191 

near  and  i.ir  points  of,  l'.)3 
Eyes,  associated  niovemenls  of,  2(M) 


Far  and  near  points  of  eye,  193 
Far-sightedness,  188 
Fatigue,  auditory,  174 

muscle,  49 
Fibrillation,  93 
Field  of  vision,  190 
Fields  for  colored  objects,  191 
I'"ish,  respiratorj'  movements,  146 
Fistula,  gastric,  218 
Fleischl's  hemoglobinometer,  74 
Formation  of  image  upon  retina,  184 
Friction  key,  27 

Frog,  gastrocnemius  of,  ergographic  rec- 
ord, .52 

heart  of,  action  current  of,  60 

otohthic  cavity  in,  181 

rhcoscopic,  59 

rotation  effects  in,  181 
I''unction  of  roots  of  spinal  cord,  103 
Fusion,  binocular,  of  dissimilar  images, 
203 

of  colors,  201 

of  gray  and  white,  201 

of  muscle  contraction,  42 


Galvanic  current,  29 

(Jalvani's  experiment,  .59 

(lastric  fistula,  218 

(!astrocn(>mius,  frog's,  ergographic  record 

of,  52 
(iastro-enterostomy,  214 
(ilossopharyngeal  nc^rves,  141 
(Jlueose,  action  of,  221 
Ciower's  hemoglobinometer,  75 
Gravity,  center  of,  39 
Gray  and  white,  fusion,  201 


Hearinc;,  173 

com|)ound  tones,  175 
location  of  tones,  174 
threshold  value  of  sounds,  174 
Heart,  acceleration  of,  88 
action,  arterial  pulse  and,  relation  be- 
tween, 129 
of  ether  and  chloroform  on,  90 
of  muscarin  on,  87 
of  nicotin  on,  87 
activities,    respiratory    activities    and, 

relation  between,  130 
apex-beat  of,  95 


234 


INDEX 


Heart  dulness,  area  of,  95 

effects  of  constant  current  on,  89 

excised,  82 

excitation  wave,  transmission  of,  81 

exposed,  inhibition  of,  114 

frog's,  action  current  of,  00 

impulse,  95 

inhibition  of,  85 
reflex,  88 

isolated  segments,  82 

mammalian,  beating,  in  situ,  91 
dissection  of,  90 

rate  of,  95 

sounds,  97 

staircase  phenomenon,  89 

Stannius'  experiment,  89 

stimulation  of,  85 

summation  of  stimuli,  89 

ventricle  of,  isolated  strips,  82 
Heart-beat,    conduction    through    ven- 
tricle, 83 

effect  of  temperature  on,  81 

normal,  79 

refractory  period,  81 

registration  of,  79 
Heart-block,  93 
Hemin  crystals,  78 
Hemocytometer,  71 

Hemoglobin  percentage,  estimation  of,  73 
Hemoglobinometer,  Fleischl's,  75 

Gowers',  75 
Hemorrhage,  71 

and  saline  injection,  effect  of,  on  blood- 
pressure,  111 

influence  of,  on  blood-pressure,  108 
Hot  and  cold  spots,  mechanical  stimu- 
lation of,  169 
thermal  stimulation  of,  169 
Hypermetropia,  188 
Hypogastric  nerves,  function  of,  225 


Illusions,  optical,  204 
relating  to  weight,  170 
thermal,  170 
Images,  dissimilar,  binocular  fusion  of,  203 
Indirect  and  direct  vision,  200 

method     for    ophthalmoscopic    exam- 
ination of  artificial  eye,  196 
Induction  coil,  29 
Inductorium,  30 
Inflammation  of  lung,  phenomena  of,  147 

phenomena  of,  147 
Inhibition  of  heart,  85 
reflex,  88 
of  reflexes  upon  central  paths,  157 
Innervation  of  bladder,  225 
Insufficiency,  aortic,  schema  of,  602 

mitral,  schema  of,  102 
Intensity  of  light  and  quality  of  color,  202 
Intestinal    juice,    secretion    of,    chemical 
stimulation  of,  218 
into  excised  loops,  219 
mucosa,  preparations  of,  histologic  ex- 
amination of,  219 


Intestine,  influence  of  adrenal  extract  on, 
219 
osmotic  power  of,  217 

Intracardiac  blood-pressure,  115 

Intrapleural  pressure,  136 

Intrathoracic  pressure,  effect  of  varia- 
tions in,  on  blood-flow  through  lungs, 
147 

Intraventricular  pressure,  schema  of,  102 

Irradiation,  203 

Irritability  of  muscle,  independent,  35 
of  nerve,  36 

Isolation  of  esophagus,  207 
of  secretory  nerves,  209 

Isometric  myograms,  34 

Isotonic  myograms,  34 


Jaundice,  experimental,  216 


Key,  simple,  26 

Kidney,  dissection  of  region  of,  222 
vasomotor  supply  of,  123 


Lacteals,  215 

Laryngeal  nerve,  inferior,  143 

superior,  142 
Laryngoscope,  176 
Larynx,  141 

interior  of,  in  man,  observation  of,  176 
Law,  all-or-none,  82 
Lens,  changes  in  shape  of,  184 

wabbling  of,  186 
Levers,  systems,  38 

Light,  intensity  of,  and  quality  of  color, 
202 
reaction  to,  165 
reflex,  184 
Localization,  cerebral,  163 

touch,  167 
Loring's  ophthalmoscope,  195 
Lungs,     blood-flow    through,     effect    of 
variations   in  intrathoracic  pressure 
on,  147 
collapse  of,  135,  136 
effect  of  decreased  atmospheric  pres- 
sure on,  148 
excised,  137 
frog's,  capillary  circulation  in,  147 

circulation  in,  147 
inflammation  of,  phenomena  of,  147 


Mammalian  heart,  beating,  in  situ,  91 

dissection  of,  90 
Mammals,  rotation  effects  in,  180 
Man,  speed  of  nerve  imi)ulse  in,  56 

vasomotor  phenomena  in,  123 
Manometer,  membrane,  115 
Marey's  pneiunograph,  129 

tambour,  91 
Mechanical  stimulation  of  hot  and  cold 

spots,  169 


INDEX 


235 


Mochanical  stimuliitioii  of  niusclf,  '2'A 

of  ri'tiiia,  HM) 
Mcilicolcfiitl  tests  for  blood,  77 
Mciiiliraiia    tyiiiparii    in    man,    ol)S('rva- 

tioii  of,  175 
Mciiihraiic  inaiioiiictcr,  IIT) 
Mcrciirv  kt'V,  2() 
Metric  wcifrlit,  229 

exact  ('(luivaleiit,  2)50 
Microscopic  examination  of  blood,  7.'i 
Mitral  insufliciencv,  schema,  102 

stenosis,  schema  of,  102 
Morse  key,  2(i 
Mosso's  er^fof^rapii,  ol 
Motion,  amel)oid,  21 
ciliary,  21 

sensation  of,  at  elbow,  171 
Motor  nerve,  irritability  near  renter,  o!) 

jjoints,  stimulation  of,  (il 
Mov(Mnent,  touch  sensations  modified  by, 
l()i) 
sinuiltanpous,  170 
Miilier-Lyor  fipiires,  205 
Muscarin,  action  on  heart,  87 
Muscle,  21 

action  current,  59 
contraction,  compound,  43 

clTect  of  excessive  stimulation  on,  49 
of  veratrin  on,  49 
on  volume,  38 
fusion  of,  42 
height  of,  relation  of  load  to,  44 

of  strength  of  stimulus  to,  43 
influence  of  blood-supply  on,  52 
of  chemicals  on,  48 
of  temperature  changes  on,  47 
method  of  registering,  33 
of  human,  51 
])aradoxic,  60 
single,  41 
siuiimation,  42 
cross-section,  relation  of  force  to,  38 
extensibility  of,  36 
fatigue,  49 

human,  law  of  unipolar  stimulation,  65 
indeijcndent  irritability,  35 
long    and    compact,    comparison    be- 
tween, 37 
manner  of  attachment  to  bones,  39 
movement,  22 
j)ower,  measurement,  37 
smooth,  53 
stimulation  of,  31 
direct.  23,  32 
indirect,  23,  32 
stimuli,  22 

relation  of  strength  of,  to  height  of 

contraction,  43 
subminimal  summation  of,  44 
tetanus,  43 

tissue,  structure  of  different  types,  21 
tonus,  160 
twitch,  41 
warmer,  47 
work,  45 


Muscle  work,  addition  of,  46 

Muscular  and  cutaneous  sensations,  lt>7 

Myograms,  isometric,  34 

isotonic,  34 
Myctgrapliy,  25,  32 

reconis  of,  fixation,  34 
Myopia,  iss 


Nkak  and  far  j^oints  of  eye,  193 

point,  18.S 
Near-sightedness,  1.S8 
Negative  after-images,  201 
Nerve,  21 

action  current  of,  60 

anodic  excitation,  ()4 

catliodic  excitation,  (>4 

chorda  tymj)aiii,  function  of,  210 

conductivity  of,  3(i 

currents,  (il 

glossopharyngeal,  141 

human,  law  of  unipolar  stimulation,  65 

hypogastric,  function  of,  225 

impulse,  speed  of,  in  cold-blooded  ani- 
mals, 55 
in  man,  56 

influence  of  temperature  on,  59 

irritability  of,  3<) 

motor,  irritability  near  center,  59 

phrenic,  137 

.secretory,  isolation  of,  209 

stimulation  of,  31 
direct,  32 
indirect,  32 

sui)erior  laryngeal,  142 

supi)lv  of  submaxillarv  gland,  .schema 
illustrating,  209 

sweat,  223 

sympathetic,  function  of,  210 

tissue,  histologic  study,  55 

trigeminal,  141 

vagus,  influence  of,  207 
main  trunk,  143 
Nerve-fibers,   conduction  in  both  direc- 
tions by,  57 
Nervous  regulation  of  respiration,  141 

.system,  1()3,  165 

frog's  dissection  of,  1,55 
localization  of  function  in,  156 
reflex  action,  155 
Neurons,  histologic  study,  155 
Nicotin,  action  on  heart,  87 
Non-polarizable  electrodes,  29 
Nystagmus,  railroad,  181 


Observation   of  interior  of   larynx   in 
man,  176 
of  membrana  tymjiani  in  man,  175 
Olfactory  cells,  distribution  of,  174 
structure  of,  174 
fatigue,  174 
latency,  174 

qualitative  changes  before  exhaustion, 
174 


236 


INDEX 


Ophthalmoniotor,  19;> 
Ophthalmoscope,  Loriiig's,  195 
Ophthahnoscopic  examination  of  ametro- 

pic  artificial  eye  by  direct  method, 

195 
of  artificial  eye  by  indirect  method, 

196 
of     ennnetro])ic     artificial     eye    by 

direct  method,  194 
Optical  illusions,  204 
Osmometer,  217 
Osmosis,  217 

Osmotic  power  of  intestine,  217 
Otolithic  cavity  in  frog,  181 


Pain  spots,  170 

Pancreas,  position  of  ducts  of,  diagram 

showing,  213 
Pancreatic  juice,  collection  of,  213 
Paradoxic  contraction  of  muscle,  GO 

resistance,  171 
Patellar  reflex  time,  16G 
Percussion,  139 

of  human  stomach,  208 
Perimeter,  191 
Peristalsis,  215,  218 

influence  of  salts  on,  218 
Phenomenon,  Babinski,  ehciting  of,  160 

Purkinje's,  202 
Phlebograph,  use  of,  129 
Phosphenes,  190 
Photic  stimulation  of  muscle,  23 
Phrenic  nerves,  137 
Pilomotor  reactions,  225 
Pithing,  23 

Placenta,  study  of,  146 
Plasma,  blood,  relative  amounts,  70 
Plethysmograph,  cardiac,  92 
Pneumograph,  Marey's,  129 
Pohl's  commutator,  56 
Polarization,  28 
Polygraphy,  129 
Positive  after-images,  200 
Posture,  effect  of,  on  blood-pressure,  127 

influence  of,  on  blood-pressure,  107 
Preparation  of  secretin,  213 
Pressure  and  touch,  peculiar  phenomena 
and  illusions  of,  168 

in  tympanum,  175 

intrapleural,  136 

intraventricular,  schema  of,  102 

secretory,  210 
Primary  current,  29 
Protoplasmic  streaming,  21 
Pulmotor,  140 

Pulse,  arterial,  character  and  velocity,  129 
heart  action  and,  relation  between, 
129 

cause  and  velocity,  schema  ilhistrating, 
103 

schema  of,  102 

venous,  character  and  velociity,  129 
Pupil,  size  of,  changes  in,  184 
Purkinje's  phenomenon,  202 


(ii'ATJTY  of  color  and  intensity  of  light, 

202 
Quickly  interrupted  current,  29 


Railroad  nystagmus,  ISl 
Rapiditj'  of  absorption  and    elimination, 
219 

of  elimination,  222 
Reaction  time,  1()5 
with  choice,  166 

to  light,  165 

to  sound,  166 

to  touch,  165 
sensation,  165 
Reactions,  pilomotor,  225 
Red  blood  cells,  human,  counting  of,  73 
corpuscles,  enumeration,  70 
simultaneous  count,  73 
Reflex,  accommondation,  184 

action,  159 
study  of,  155 

centers  for  hind  legs,  localization  of,  156 

light,  184 

time,  157 
patellar,  166 

winking  time,  166 
Reflexes,  action,  159 

exaggeration  of,  by  means  of  strychnin, 
159 

in  man,  159 

inhibition  of,  by  higher  centers,  159 
upon  central  paths,  157 

spreading  of,  157 

tendon,  in  man,  160 
Relation  of  weight  to  area  stimulated,  170 
Resistance,  paradoxic,  171 
Respiration,  133 

accessory  movements,  141 

action  of  thorax  in,  134 

artificial,  140 

center  of,  localization,  145 

elimination  of  carbon  dioxid  in,  151 
of  water  in,  151 

forced,  135 

frequency,  139 

glossopharyngeal  nerve  in,  141 

inferior  laryngeal  nerve  in,  143 

influence  of  carbon  dioxid  in,  140 

larynx  in,  141 

main  trunk  of  vagus  nerve  in,  143 

mechanics  of,  133 

nervous  regulation  of,  141 

normal,  134 

placenta  in,  146 

self-regulation,  141 

superior  laryngeal  nerve  in,  142 

trigeminal  nerve  in,  141 
Respiratory    activities,    heart    activities 
and,  relation  between,  130 

movements  in  fish,  146 
R(!tina,  formation  of  image  upon,  184 

mechanical  stimulation  of,  190 
Retinal  blood-vessels,  199 

image,  formation  of,  186 


iNi>i:x 


2:i7 


Ulicoscopif  froK,  ^^ 
Hiva-K«><"«'i's  spliynmomanoinotor,  121 
Udots  of  spinal  cord,  fimclion  of,  Id.) 
Rotation  i-ffcots  in  frofi,  isl 

in  inanunals,   ISO 
Rotatory  api)aratus  for  color  disks,  2  '1 


Sai.ink  injection  and  licniorrliajic,  clTi ct 

of,  on  hiood-pn'ssurc.  Ill 
Saliva,  secretion  of,  2(Kt 
Salivary  glands,  dissection  of,  211 
Salts,  inlliieyce  of,  on  peristalsis,  21 S 
Scheiners  experiment,  ISIl 
Sciatic  nerve,  vasomotor  action  of,   lis, 

119 
Secondary  cinnMit,  2i) 
Secretin,  action  of,  21 1 

prejiaration  of,  2i:> 
Secretion  hy  bloodless  ^laiid,  210 

normal,  of  urine,  221 

of  l)ile,  21.") 

of  intestinal  juice  into  excised  loops,  21!) 

of  saliva,  2()!» 

of  sweat,  22;i 
Secretory  nerves,  Lsolation  of,  209 

pressure,  210 
Semicircular    canals,    action    of,    model 
illustrating,  ISO 
position  of,  179 
Sen.sation  of  motion  at  elbow,  171 
Sens(>  organs,  1G7,  1715 
Shadow  test,  19() 
Shape  of  lens,  changes  in,  184 
Simultaneous  movements,  170 
Single  and  double  images,  203 
Size  of  pupil,  changes  in,  184 
Skia-copv,  190 
Smell,  173 
Smooth  muscle,  53 
Snellen's  test  types,  194  ' 
Sodium  chlorid,  action  of,  221 
Solidity,  judgments  of,  relation  of  binocu- 
lar vision  to,  203 
Sounds,  reaction  to,  166 

threshold  value  of,  174 
Specific  gravity  of  blood,  75 
Spectroscopic  examination  of  blood,  77 
Spheric  aberration,  190 
Sphvgmograph,  application  of,  129 

Didgeon,  129 
Sphygmomanometer,  application  of,  125 
Sphygmotonometer,  125 
Spinal  cord,  roots  of,  fvmction  of,  163 
Spirometer,  133 
Splanchnic    nerve,    greater,     va.somotor 

action  of,  121 
Spot,  blind,  199 

contours  of,  199 

pain,  170 

yellow,  199 
Spring  ergograj)!),  52 
Staircase  j)henoinenon,  S9 
Stannius'  experiment,  89 
Static  and  dj'namic  senses,  179 


Stenosis,  aortic,  schema  f»f,  102 

mitnd,  schema  of,  102 
Stethograph.  Mareys,  I.'IO,  131 
Sletliograpliy,  139" 
Stimulating  ele<'tro<les,  27,  2S 
Stimulation,  excM'ssive,  «'ffect    on    muscle 
contraction,  49 
of  cerebrum.  Hi:', 
of  muscle,  :il 
<lirect,  32 
indirect,  32 
of  nerve,  31 
din-ct,  32 
indirect,  32 
threshold  of,  160 
Stimulus,  inadeciuate,  173 

mu.scle,  relation  of  strength  of, 
to  height  of  contraction,  43 
subminimal,  sununation  of,  44 
thermal,  effect  of,  1.57 
Stomacii  contents,  21() 

hmnan.  percussion  of,  208 
Streaming,  pnjtoplasmic,  21 
Strychnin,    exaggeration    of    reflexes   by 

means  of,  159 
Submaxillary    gland,    nerve    supply    of, 
schema  illustrating,  209 
vasomotor  changes  in,  jjroduced  by 
stimulation  of  chorda  tympani  and 
sympathetic;  nerve,  210 
Sweat  nerves,  223 
secretion  of.  223 
Sweating  in  man,  223 
Swim  test,  137 

Sympathetic  nerve,  cervical,  vitsomotor 
action,  117 
function  of,  210 


Tactile  corpuscles,  histologic  examina- 
tion of,  167 
Tambour.  Marey's,  91 
Taste,  173 

distribution  of,  173 

electric  stimulation,  173 

elimination  of  sweet  and  bitter,  174 

inadequate  stimuli.  173 

reaction  to  single  papilla.  173 

threshold  value  of,  173 
Taste-buds,  structure  of,  173 
Tears,  entoptic  phenomena  produced  bv. 

192 
Temperature,  after-image  of,  169 

body,  223 

changes,  influence  on  muscle  contrac- 
tion, 47 

contrast,  170 

effect  of,  on  heart-beat,  80 

influence  of,  on  nerve,  59 

sense,  acuity  of,  170 

spots,   chemical  and  electric  stimula- 
tion of,  169 
Tendon  reflexes  in  man,  160 
Test,  swim,  137 

types,  Snellen's,  194 


238 


INDEX 


Tetanic  current,  29 

Tetanus,  incomplete,  of  heart,  89 

nuiscli\  4;j 
Thermal  illusions,  170 

stimulation  of  hot  and  cold  spots,  169 
of  muscl<»,  23 

stimuli,  etfect  of,  157 
Thoma-Zeiss  hemocytometer,  71 
Thoracic  duct,  216 
Thorax  in  respiration,  action  of,  134 
Tones,  compound,  175 

location  of,  174 
Tonus,  muscle,  160 

Touch  and  i)ressure,  peculiar  phenomena 
and  illusions  of,  16S 

discrimination,  167 

localization,  167 

projection  of  sensation  of,  169 

reaction  to,  165 

sensations,  adaptation  to,  168 
modified  by  movement,  169 
reaction  to,  165 
Traube-Hcring  curves,  106 
Trigeminal  nerves,  141 
Twitch,  muscle,  41 
Tympanum,  pressure  in,  175 
Types,  test,  Snellen's,  194 

UxiPOLAR  stimulation  of  human    muscle 

and  nerve,  law  of,  65 
Urine,  flow  of,  drop  method  of  registering, 
221 

normal  secretion  of,  221 


VACii  nerves,  both,  division  of,  effect  of, 
on  blood-pressure,  114 
influence  of,  207 

intact,  stimulation  of,  effect  on  blood- 
pressure,  113 
Vagus  nerve,  one,  division  of,  effect  on 
blood-pressure,  114 
main  trunk,  143 
Valves,  venous,  position  and  function,  109 
Vasomotor  action  of  cervical  sympathetic 
nerve,  117 
of  depressor  nerve,  118 
of  greater  splanchnic  nerve,  121 
of  sciatic  nerve,  118,  119 


^^asomotor  changes  in  submaxillary  gland 
produced  by  stimulation  of  chorda 
tymi:)ani  and  sympathetic  nerve,  210 
phenomena  in  man,  123 
supply  of  kidney,  123 
Venous  blood,  6S 
blood-pressure,  128 
pulse,  character  and  velocity,  129 
valves,  position  and  function,  109 
Ventricle  of  heart,  conduction  of  heart- 
beat through,  83 
isolated  strijjs,  82 
Veratrin,  effect  on  muscle  contraction,  49 
Vision,  183,  189,  193,  199 

binocular,  relation  of,  to  judgments  of 
direction,  203 
of  distance,  203 
of  solidity,  203 
field  of,  190 
Visual  angle,  194 

axes,  converg(>nce  of,  influence  of,  203 
Vocal  cords,  abduction  of,  143 
and  adduction  of,  143 

Wabbling  of  lens,  186 
Warmer,  muscle,  47 

Water,  elimination  of,  in  respiration,  151 
Wave  of  deglutition,  207 
Weber's  law,  170 
Weight,  apothecaries',  229 
exact  equivalent,  230 

discrimination  of,  Weber's  law,  170 

illusions  relating  to,  170 

metric,  229 

exact  equivalent,  230 

relation  of,  to  area  stimulated,  170 
Weights  and  measures,  229 
White  and  gray,  fusion  of,  201 

blood  corpuscles,  enumeration  of,  71 
Winking  time,  reflex, 
Wintrich's  modification  of  Hutchinson's 

spirometer,  133 
Work,  muscular,  45 
addition  of,  46 
Work-adder,  45 

Yellow  spot,  199 

Zollner's  lines,  204 


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